Can online casino games such as roulette and blackjack or even poker be trusted?

Im particularly interested to know about roulette because i enjoy it the most!In my local casino i know its basically 50 50 when the ball spins but id like to think its like that online too?Surely its illegal for the people who run these sites to tamper with the games and essentially just rob the people who play them because that would be just daylight robbery!Can they be trusted or can they just rob people and get away with it?