The interesting thing about roulette is that the numbers are distributed unevenly. If you make thousands of spins, all the numbers will fall approximately equally often, on average once every 37 spins. In the short run, however, this is not the case. Some numbers repeat frequently and others take quite a long time to fall. That's a fact. Roulette will never behave predictably, but even in this randomness, certain patterns can be traced. Some strategies try to bet on repeating numbers, while other strategies bet on numbers that have not fallen for a long time, because sooner or later they will also fall (and after a while they will also start to repeat). Both approaches can be correct and both can fail. Basically, every time you spin, there is still the same probability that something will fall, regardless of what fell before. Each strategy exists in many different modifications to suit each player's taste and setup.