Putting your entire iTunes library onto shuffle and just leaving it to play, even though there is a lot of random music that you forgot you had/is embarrassing/is audiobooks or podcasts amongst your preferred song choices. iTunes roulette is a game generally played when (individually or as a group) you can't decide what song to put on, because making a playlist is faaaarrr too much like hard work
:Whoa! Why the fuck are you guys listening to The Ketchup Song?
:Barely even realised, because we were playing iTunes roulette.
:Hey, I didn't know you liked ACDC
:Yeah, they're awesome. I like how iTunes roulette has just brought us closer together