How to make an RNG game on Roblox

RNG games, where the core action is rolling for a random aura, title, item or character, became one of Roblox's breakout genres. The loop is tiny: roll, see what you got, roll again. That makes them fast to build and easy to get wrong, both in how the maths works and in how you sell luck. This guide covers both.

Why the loop works

An RNG game is a collection game driven by anticipation. Players keep rolling because:

• Every roll might be the one. A tiny chance of something rare is exciting every time.
• Rarity is visible. "1 in 1,000,000" next to an item tells everyone how special it is.
• Showing off is the reward. Rare rolls are announced to the server, worn on the avatar and posted in clips.

Everything in your design should feed one of those three.

Build a weighted rarity table

Each item gets a weight, and the chance of rolling it is its weight divided by the total. Writing chances as "1 in N" is natural for this genre, so store that and convert:

local ITEMS = {
	{ name = "Common", oneIn = 1 }, -- what you get if nothing rarer hits
	{ name = "Uncommon", oneIn = 8 },
	{ name = "Rare", oneIn = 64 },
	{ name = "Legendary", oneIn = 1000 },
	{ name = "Mythic", oneIn = 100000 },
}

local rng = Random.new()

local function roll(luck)
	-- Try rarest first; luck divides the odds (2x luck turns 1 in 1000 into 1 in 500).
	for i = #ITEMS, 2, -1 do
		local item = ITEMS[i]
		if rng:NextNumber() < luck / item.oneIn then
			return item
		end
	end
	return ITEMS[1]
end

This "rarest first" approach is popular in RNG games because luck is easy to understand: 2x luck halves the odds of everything rarer than common. The displayed "1 in N" is a little off from the true chance, because each rarer tier is tried first, but the gap is tiny for rare items. If you want displayed odds to be exact, use a normalised weighted pick instead, and recompute the displayed odds from the same table.

Whichever method you use, run the roll on the server and keep one source of truth for the odds you show players.

Make luck feel real

Luck is the genre's main progression and its main product, so it has to visibly work:

• Show the player's current luck and what it does to each rarity.
• Stack sources clearly: a base luck, a temporary potion, a pass, a server event. Show the total.
• Use a pity or guaranteed milestone (for example, every 1,000th roll is at least Rare) so unlucky players still progress.
• Keep luck boosts honest. If a boost says 2x, it must double the chance you show, not something vaguer.

Make rolling satisfying

The roll is the action players repeat thousands of times:

• A short animation that cycles through possible results and lands, with sound.
• Bigger celebrations for rarer results: colour, screen effects, a server-wide announcement for very rare rolls.
• Quick rolls and auto-roll once a player has seen the full animation many times, so the game respects their time.

Give the collection meaning

Rolling is more fun when results do something:

• Equippable auras or titles that other players can see.
• An index that tracks what the player has found, with rewards for completing tiers.
• Crafting, where duplicates combine into something new, so common rolls still have value.
• Leaderboards for rarest find and total rolls.

Save carefully

Players may spend hours chasing one rare result, so a lost save is devastating. Save inventory and roll counts with DataStoreService on a timer, when the player leaves and on shutdown with game:BindToClose, and never let a failed load start a player on an empty save that could overwrite their real data.

Paid random items: the rules

This is the part most RNG games need to get right. If players spend Robux for a random result (paid rolls, paid eggs, paid crates), Roblox's policies require you to show the odds before purchase. Some countries restrict paid random items altogether, and Roblox exposes that through PolicyService:GetPolicyInfoForPlayerAsync, which returns whether paid random items are restricted for that player. If they are, don't offer the purchase.

Paid luck boosts change the odds of a random outcome, so treat them with the same care: show exactly what they do, and check the policy flag before offering them. Read the current PolicyService reference and Roblox's monetisation policies before launch. Selling convenience (auto-roll, faster rolls, extra storage) avoids most of these issues.

Game passes vs developer products explains how to set up each kind of purchase, and monetising without driving players away covers pricing.

Checklist

• Rarity table with clear "1 in N" odds, rolled on the server
• Displayed odds match the real ones; luck shown and stacked clearly
• Pity or milestone guarantees for unlucky players
• Satisfying roll with bigger celebrations for rarer results; auto-roll later
• Collection that matters: equippables, an index, crafting, leaderboards
• Saves on a timer, on leave and on shutdown
• Odds shown for any paid random item; PolicyService checked before offering

RNG games rise and fall quickly, so it pays to watch the ones growing right now. BloxIQ's outlier scores flag games growing well above their usual level, and the Chrome extension shows player trends on every game card as you browse Roblox.