Let's start with the game basics to get the general idea of how to play roulette.
The aim of the game is to guess the slot number where the ball will land. The player plays against the dealer, who is responsible for spinning the wheel, the ball and paying out the wins. European wheel has 36 numbers and a 0 slot, while American roulette has 36 numbers, 0 and 00 slots. To read about American and European roulette take a look at the Roulette variations.
Each player (up to 8 at one table) change the money for special roulette chips which are of one color for every player. This is done not to mix them up. Online roulette does not change the color as it is always one player at the table.
Players place their bets on the roulette table. The bets may be on one number, two numbers, 3, 4, 5, 6, 12 numbers or on the color of the number (red or black) on whether the number will be odd or even, whether the number is small (1-18) or big (19-36).
The dealer spins the wheel and launches the ball. When the dealer announces NO MORE BETS the players are not allowed to place bets anymore. As soon as the ball lands, the dealer announces the winning number and pays out all the winning bets. All the bets that did not win are lost to the casino.
The object of roulette is to predict or guess where the ball will land. The ball lands randomly therefore the next spin does not depend on the previous ones.
As you can see the rules of how to play roulette are pretty simple and need to special knowledge or training.