Takes place whenever you're in the need of toilet facilities and are
a) entering a booth or
b) raising a toilet seat cover.
You loose in toilet-roulette if the toilet is blocked and full of yuk.
The chances for loosing in toilet-roulette are usually lower in the morning, and increases for every opening hour. In extreme cases the odds for loosing are above 9/10.
B: Agh. Fuck it. You can have my lunch bag. I was suppose to take a quick wee before I met you, but lost toilet-roulette 7 times, and now I'm too disgraced to eat my lunch.