I think with magnets in the roulette, the ball that falls on the number is rigged. Magnets pull the ball to the number that is probably rigged with some kind of computer system.
I believe you speaking of land-based casinos aka physical casinos. In this forum we are mainly discussing about bitcoin/altcoin accepting casinos and thus physical casinos are out of the picture - I dont know any physical casino which is accepting bitcoin or altcoin till date.
When you are not gambling on real presence, you should go with provably fair. When the game outcome are locally influenced, to some extent every dealer would have some level of influence on the outcome.
All the popularly know sites where people gamble are provably fair. With provably fair every casino would be a scam and anyone playing there is a fool to trust the system. Provably fair makes every roll mathematically fair and thus making it unbiased.