Roulette sucks. Plain and simple. Sometimes the wheel will spin slower than normal so you'll have to improvise/wing your timing. But if it's going at the normal, FAST speed, here are a couple visual and timing queues I and other runners use to get roulette about a third of the time (WHICH IS ACTUALLY REALLY GOOD).

BETTING ON 16 This is the strat that WR holder Konasumi uses. After betting on 16, accelerate and rocket boost as the double green 0s pass the car.

BETTING ON 3 If you're betting on 3, like me and basically only me, accelerate and rocket boost as soon as the single green 0 goes fully off the screen to the right.

MAKING YOUR OWN Hey you can do that if you want. I don't know why you'd wanna spend more time on roulette than you need to, but you can.

Again, the roulette wheel can be very inconsistent with speed, so you might have to adjust your timing a bit if you can tell that it's spinning slower than normal. If not, just grind runs until you get good rng :^) gl