There’s no way to get an edge at roulette.
I should amend this to say that there’s no realistic, practical way of getting an edge. Players have gotten an edge at the game, but it’s not something the average person can learn to do easily. (If you’re looking for a gambling strategy that anyone can learn, consider counting cards in blackjack.)
Most players try to get an edge by using some kind of betting system that involves raising and lowering the size of their bets based on the previous results on the wheel.
The problem with these betting systems is that past results have no effect on the probability of future results. That seems counter-intuitive, but that’s how the math of the game works.
Look at it this way:
You’re playing roulette, and the ball has landed on black 5 times in a row.
What is the probability that the ball will land on black on the next spin?
Since there are still 18 black outcomes and 37 total possible outcomes, the probability is STILL 48.65%. It hasn’t changed because of the previous results.
It’s counter-intuitive because the probability of getting a black result 6 times in a row is something that can be measured, and it is unlikely.
But you’re not betting on whether or not the ball will land on black 6 times in a row. You’re betting on what’s going to happen on the next spin.