RTP is a term that is very commonly used in Casinos and gambling. RTP stands for Return To Player and it describes the amount a slot pays back to the players over a large number of spins, usually expressed as a percentage. To better understand how it works, a slot with RTP of 96% will give back $96 for every $100 that goes into it. Online Casino cannot manipulate the RTP because the games themselves are stored on the servers of the developers and Online Casino have no way to change the RTP.
The roulette with the highest RTP is the french Roulette (98.65%), the European Roulette (98.37%), the lightning roulette (97.3%).