To make money playing roulette, correctly guess the number or type of number the ball will land on when the dealer spins the wheel. In a roulette round, play starts after the dealer clears the table of the previous game. At this time, place your bets on your desired number slots.

Seriously: roulette is random, every number has equal chance of winning. From pure probability theory you can calculate what is the probability of winning, no luck involved. I define "luck" as the difference between average expected results to actual results. In the long run it's zero.