For a game like roulette, the online casinos will have a live dealer (or sometimes just a live wheel where the ball gets inserted automatically). All your bets are placed on your phone screen but the wheel spins in real life, and then the result is seamlessly digitized, so you're paid out immediately.

The virtual roulette is a piece of software that emulates a real roulette. Once a player places their bet, the software generates a random winning number which ranges between 0 and 36. To do this, a pseudorandom number generator (PRNG) is used [3].