How to make an RNG game in Roblox Studio

RNG games are built around one button: roll. Each result has a rarity shown as “1 in X”, and the fun is chasing the rare ones. The roll must happen on the server, and the odds you show must be the odds you use.

The core loop

Every RNG game comes down to one loop that players repeat. Build this first, in grey blocks:

1. Roll
2. Get a result with a visible rarity
3. Equip or collect the best one
4. Use luck boosts to roll for rarer results

Systems you need

Build order

1. 1

   Rarity table and roll

   The script below, tested with prints.

2. 2

   Roll button and animation

   A ScreenGui button that calls the RemoteFunction and plays a short reel.

3. 3

   Inventory and equip

   Save rolled results; show the equipped one as a BillboardGui or effect.

4. 4

   Luck and auto-roll

   Luck potions and an auto-roll toggle (still limited by the server cooldown).

The key script: Server-side “1 in X” roll with luck

Where it goes: ServerScriptService > Rolls (Script).

• Insert a RemoteFunction named Roll into ReplicatedStorage.
• A LocalScript calls Roll:InvokeServer() and shows the returned name.

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local Players = game:GetService("Players")

local rollRemote = ReplicatedStorage:WaitForChild("Roll")

-- "1 in X" chances, rarest first. The first is the fallback and always hits.
local RESULTS = {
	{ name = "Celestial", oneIn = 10000 },
	{ name = "Mythic", oneIn = 1000 },
	{ name = "Legendary", oneIn = 250 },
	{ name = "Epic", oneIn = 50 },
	{ name = "Rare", oneIn = 10 },
	{ name = "Uncommon", oneIn = 4 },
}
local FALLBACK = "Common"
local COOLDOWN = 1
local random = Random.new()
local lastRoll = {}

local function roll(luck)
	for _, result in RESULTS do
		if random:NextNumber() < luck / result.oneIn then
			return result.name
		end
	end
	return FALLBACK
end

rollRemote.OnServerInvoke = function(player)
	local now = os.clock()
	if now - (lastRoll[player] or 0) < COOLDOWN then
		return nil
	end
	lastRoll[player] = now

	local luck = player:GetAttribute("Luck") or 1
	local result = roll(luck)
	-- Save it to the player's inventory here.
	return result
end

Players.PlayerRemoving:Connect(function(player)
	lastRoll[player] = nil
end)

How it works

• Checking rarest first means a result's chance is close to luck / oneIn for rare entries, which is what the “1 in X” label promises.
• Common results are slightly less likely than their label because rarer checks come first — round labels on commons accordingly.
• Use one Random.new() object on the server; never let the client send the result or the luck value.

How RNG games make Robux

• Luck boosts (timed developer products) and a permanent 2× luck game pass.
• Faster roll speed or auto-roll as a game pass.
• Show the real odds next to anything that boosts luck — players and Roblox expect paid random items to be transparent.

You receive 70% of what players spend on game passes and developer products; Roblox keeps 30%.

Common mistakes