RPG players sure do love their dice. In the handful of years that I’ve been playing and GMing games, I have seen (at least) one player at (almost) every table deploy an astronomical number of math-rocks; tidy unit formations of nerd-pebbles that make my GM-sprawl look downright spartan. Of course each of those varieties of dice serve different purposes: these are for spell-casting, those are the “roleplay” dice, this one is sentimental, that set is moral support… If you haven’t noticed this behavior then likely it is you whom the power of dice compels.
The affinity goes beyond acquisition. Players contemplating some action habitually fiddle and finger their dice rosary beads, willing the polyhedrons to bless their intent with auspicious numbers. A die that falls favorably is lauded above its peers, while one that disappoints is banished to contemplate its shame.
As much as the probability-fetish can amuse, it falls a short when we try to understand “first principles” of gaming. The dice never tell us Why, they never make clear the reason for rolling dice in the first place.
A mechanical answer to the question (“why do we roll dice?”) is as straightforward as they come: dice provide a random value that is useful for determining game outcomes. When you boil it down that far, any sufficiently formalized game system is indistinguishable from gambling! This is a literal reductio ad absurdum that requires a particularly-motivated thinking (or supremely superficial observational skills) to arrive at, but it is useful regardless. There is a fundamental difference between RPGs and games of chance: the purpose of an RPG, even from their earliest days, is to tell a story.
That’s important enough to repeat: “the purpose of an RPG is to tell a story”. The first edition of Dungeons & Dragons, broadly regarded as the world-first RPG, emerged from a union of medieval fantasy literature and table-top war gaming. Those 1970’s tabletop war games were historic re-enactments of famous battles - and a re-enactment is nothing if it’s not the telling of a story. Gettysburg, Waterloo, and D-Day are battles, but they’re also stories that people tell years, decades, centuries later. While there are some famous card games that have become (or were central to) stories - the “Dead Man’s Hand”, Casino Royale’s baccarat (or Hold 'Em) games, episodes of Maverick - the reality is that ESPN isn’t (we all hope and pray) about to foist on us a channel of “classic” World Series of Poker reruns. More to the point, no one is much interested in the historic re-enactment of a night of table games at the Bellagio - the activity of the games may look similar, but the motivations are entirely different.
When our motivation is to tell a story, our activities are in service of that telling. We (often, typically) roll dice in an RPG to determine the outcomes of our actions, stringing together one outcome after another into a larger, more complex narrative. We use dice (and other sources of randomness) because the unpredictable back-and-forth, up-and-down, win-and-lose randomness is exciting. The uncertainty of not knowing the end, the way there, or who someone truly is, engages our curiosity and gives us problems to solve, outcomes to strive toward, conditions to hope for, as well as consequences to fear, results to dismay. Going to the pharmacy to pick up a prepared prescription isn’t interesting, it is literally a chore - but it becomes a story when it meets the unexpected: the pharmacist was wearing a funny mask, the parking lot was closed to be resurfaced, a pet raccoon appeared to be pulling into the drive-through. Prophecies are only interesting because they are unlikely, forecasts only make the front page when they’re extraordinary.
Uncertainty is the root of interest. Storytellers carefully modulate uncertainty to avoid too little (boredom) and too much (anxiety). RPG players are storytellers, shaping our parts of the imagined world through actions (but not necessarily outcomes) of our choosing - increasing and decreasing uncertainty at turns throughout our gaming sessions, losing interest with obvious, railroaded outcomes and becoming overwhelmed with “empty solution paralysis” when no map, rumor, or NPC is available to suggest the next step.
Within the context of a story, we have both useful and irrelevant types of uncertainty. We’re never told, for example, the middle name of the narrator of Catcher in the Rye. Despite the uncertainty of knowing that his given name is Holden, that he hails from a family of Caulfields, we’re never capable of knowing whether the young man is in possession of a middle name - much less what it is (turns out it’s “Morrissey” which goes a long way to explaining why his obnoxious plaintive moaning). This trivia adds nothing to the text, provides no insight to the mind of a disaffected youth, and only serves for making snarky comments about the frontman of the Smiths. Conversely, J.R.R.'s title to The Hobbit, or There and Back Again is positively brimming with useful, engaging, intriguing uncertainty. Never mind our memoirist making it back again, we have questions: where is the “there” of the going to?; what, exactly, is a hobbit?; what adventures must have warranted such a memoir, such a title?!
The “useful” uncertainty in a story has a proper name: dramatic tension and it is the essential, defining element of a story. Our routine trip to the pharmacy for a known-ready prescription has no tension dramatic or otherwise, that’s how we know it’s not a story. Bilbo’s journey to the Lonely Mountain (and back again) is chock-a-block with dramatically tense scenes from uninvited guests, hungry trolls, gathered armies, and a marauding dragon. Even knowing that Mr. Baggins is destined make it back again does nothing to prevent us from wondering just how it is that he extricates himself from this latest disaster.
Tolkien was one heck of a storyteller, enough so that a decade and a half later Gary Gygax was building an entirely new method of storytelling off his work, eventually enlisting tens of millions of us into this novel technique. We the players, as co-storytellers, don’t passively receive events-as-narrated, we make choices for our characters and declare their actions. We want our characters to prevail, to win the game, to achieve fantastical things, and we accept that those triumphs are only interesting, only matter, when there is a possibility of failure for them to overcome. Even then, the risk of failure alone is not enough, the intensity of the outcome is amplified by the stakes. No heroes are lining up for “I saved the multiverse and all I got was this lousy t-shirt”, and no villains are content with merely raising a “bad neighbors” banner for the king to look at in impotent confusion.
As players, we can’t be trusted to choose our own misadventures. We have an interest in guiding our characters to victory, but we also have an interest in engaging with an exciting, meaningful story. We have a conflict between these two interests; we have tension between these competing, conflicting desires. The story gains meaning and excitement when our in-game actions can succeed or fail, when the likelihood of those outcomes is uncertain. We are most engaged when “[our] Quest stands upon the edge of a knife. Stray but a little and it will fail, to the ruin of all”, when the risks our characters face are commensurate to the stakes of their success or failure.
We roll dice to manage the uncertainty of character actions, to settle the tension between our competing desires, to force an outcome into the narrative. Probability is the edge of the knife that we stand upon.
Dice rolls have definite, certain outcomes and they cause a decrease in the overall uncertainty in a situation. This causes a resolution - a release - of some of the dramatic tension as the success (or failure) shrinks the domain of possible actions available to all of the acting entities within the story. Bilbo falling through darkness is dramatically tense and full of uncertainties: where he will land, whether he will survive, and what he will find are all unknown. Landing in relative safety resolves the tension of his fall, but exposes new uncertainties.
Our stories, the ones that we construct together at the game table, move in the same way. Tension increases and decreases, building and releasing like a heartbeat pumping and driving from one scene, one decision to the next.
There is a balance that we have to manage. Imagine your story - for the scene, the session, the campaign - as a balloon. As you fill the story with possibilities and uncertainties, you are inflating the balloon. The surface of the balloon is expands, drawing tighter and tighter in the same way that all of those uncertainties increase the dramatic tension in the story. Letting air out of the balloon eases the tension, just as removing possibilities and resolving uncertainty does for dramatic tension. Fill the balloon too much and it reaches a point that it bursts, the surface tension becomes too great to maintain and all of the potential, all the possibility rapidly escapes. Watching the balloon fill and fill, expanding, stretching its skin thinner and thinner, waiting for the breach, is anxiety-inducing. Under-filling the balloon, or letting all the air out of it, leaves it empty, useless, flaccid… boring.
RPG players love their dice, and they love to roll them, but the results of those dice reduce the tension in our story-balloon. When we jump to rolling dice too readily in a scene, we risk leaving our balloon empty, boring, and meaningless. Over-filling our story-balloon with an ever-accumulating expansion of possibilities risks a spontaneous, unplanned release of tension, abruptly ending the over-extended story.
This is not a perfect metaphor, or perhaps it would be more appropriate to say that it an imperfect formulation of the metaphor. Rolling dice is not the only way to release the tension caused by uncertainty: making rulings does so as well. GM declarations of success or failure have the exact same effect: certainty is injected in the story and overall dramatic tension is reduced. In reality, “GM fiat” is even less satisfying, even more boring, than the empty, over-rolled balloon - at least someone got to do something when we were rolling dice!
We find ourselves with another tension to manage, one that runs between the arbitrariness of the dice and the capriciousness of the GM. If anything, managing this conflict might be more subjective than we saw with dramatic tension, making it more difficult to pin down a reliable heuristic.
Different games give us some guidance on this task, but I’m afraid to say that seems to boil down to “Use your best judgment”.
Star Trek Adventures doesn’t offer us much help here, leaving it up to the GM to decide how to resolve the action and suggesting either a dice roll, a series of dice rolls, or “some other challenge”.
The Last Caravan is more helpful with the instruction that “[d]ice don’t get rolled until there’s something at stake” - which at least establishes some sort of rational test. (-- folks, I am huge advocate for this game and recommend it for everyone. I am currently derelict in tabling a caravan finale and need provoked in that regard --)
The Dungeons & Dragons 5.5e (this is still a terrible name) core books (yes both the PHB and the DMG) actually offer some actionable advice on the subject. Here’s what the 2024 revision of the Dungeon Masters Guide says on the subject (p. 27, emphasis mine):
If the task is trivial or impossible, don’t bother with a D20 Test. A character can move across an empty room or drink from a flask without making a Dexterity check, whereas no lucky die roll will allow a character with an ordinary bow to hit the moon with an arrow. Call for a D20 Test only if there’s a chance of both success and failure and if there are meaningful consequences for failure.
This is a logical test that can bear some scrutiny, even if it rests on some subjective rulings.
A player who insists that their character should lie about their name to NPCs probably expects to make a Charisma (Deception) check over the falsehood. There are chances for both success and failure, but it’s possible that there are no stakes, no “meaningful consequences” for the outcome. Succeeding on the roll results in the NPC calling the character by the wrong name. Failing the roll might degrade a relationship between the two, but it’s every bit as likely that the NPC might just conclude there is a reason behind the assumed name and take no offense. Either way, it would be strangely disruptive for anyone to become hostile over a lie this inconsequential - no test, no dice roll, is needed here.
Consider another situation. A Rogue wants to free climb 20’ of castle wall, and do so as soundlessly as possible. They are capable of the movement for it, and are a talented sneak. They are all alone, and under no physical threat, so the climb is clinched and Just Happens 
. There are no entities that are capable of perceiving the area. It’s not really possible to fail on the player’s objectives here.
A dice roll could be a shake-up in either of these cases, but there are no mechanical reasons to call for one. Why break the action when it means disrupting stakes-building? It’s a purely discretionary ruling - a dice roll doesn’t need to happen so it demands a really good reason to justify calling for one.
The frequency of dice rolls is going to vary depending on the GM and the complexity of player choices. Be vigilant against setting up “rolling to failure” test sequences, where players have to repeatedly re-roll in order to maintain or preserve an earlier success. There are alternative ways to handle this, such as an action clock that accumulates only successes or failures (The Last Caravan uses these as a core element), an Extended Task (as from Star Trek Adventures 2E), or simply allow the first success to remain in effect through the scene. However you choose to manage it, pay attention to how that choice affects the dramatic tension in the scene and optimize for a fun balance of tension - even if that means skipping (or calling for) some dice rolls.
