There is/are no bets, no combinations of bets, no series of bets that can ever yield a positive return. It is a game of independent trials - previous results do not affect future results. Look up the world records, I think the same number has been spun in 9 times in a row or something stupid.
The only ways to beat roulette are -
The wheel to have a bias and you to know this and exploit it.
Capping bets, ie palming more cash onto winning bets etc.
Using devices to predict where the ball will land, people have done this and been caught.
Basically the only way to win is cheating.
If you wanna study a casino game you can actually beat legally with skill have a look at blackjack.
www.wizardofodds.com is the best gambling site on the net I think. It'll tell you all you need to know.