This will provide you an answer in regards to gambling or arcades in general. If you’re looking for specifics about what machines you cannot make, it’s heavily context dependent. Nothing inappropriate obviously and nothing that involves Robux. From there, it’s just thinking logically about what wouldn’t be appropriate to put down in a Roblox game.
So long as it is purely earnable, yes. No Robux can be involved in any way, directly or indirectly, with your arcade systems. Your algorithms must also be fair and not rigged for the player to lose.