I think casinos exist elsewhere. But yeah, roulette works for casinos by making the payouts slightly less than the actual odds. A black or red bet pays 2 to 1, but there’s a 5.3% chance it lands on either of the green spaces and all black and red bets lose. Theoretically, a lucky player could break the house (there’s a Star Trek episode where this happens), but on average the casino just makes money.