If you play roulette in illegal casinos, I suggest doing research so you know what the wheel looks like. In fact anyone can purchase a roulette wheel with magnets from a supplier in China.
The only casinos I know use magnets are unlicensed by the government. Which Casinos Use Magnets in Roulette Wheels?
And remember that legal doesn’t necessarily mean moral. Generally it doesn’t happen in a government sanctioned casino because if they were caught, they would lose their gambling license and face heavy fines. Of course though, governments in different countries have different ideas on what should be legal. Often people ask me if casinos ever use rigged roulette wheels with magnets. The truth is some wheels do have magnets, and some casinos do cheat players.