Are games where players can exchange in-game items for Robux against TOS? (for example, players get 1 Robux for 100 in-game coins, some sort of web backend automatically processes mass group payouts at the end of each day)
I read through the Roblox TOS and Guidelines recently and I wasn’t entirely sure if this sort of system would be compliant or not. I noticed there are games where people sell in game items like paintings for Robux to other users via UGC Clothing (see: Starving Artists on Roblox) which seems like a roundabout way of allowing players to earn Robux through a game
Yes.
You are not allowed to host giveaways on Roblox with Robux. Which means you cannot exchange in-game currency with robux.
You can certainly pay a contributor who played your game so much that he gave true help, then paying him could be qualified as a commission payout.