A ball is dropped onto the wheel, and where it lands when the spinning stops will determine whether you have won the game. When you play free roulette, you make your bet and click the button to spin the wheel. Similarly, all wagers are the same, and all payouts are the same for your bets.
The gameplay is identical and includes a wheel, ball, and betting table. Online free roulette is the same game you play when you play real money online roulette or even roulette at a land-based casino.