roll for initiative 

Comes from tabletop games and other games that use dice in combat mechanics. Generally, when a big fight is about to go down, players will "roll for initiative" and whoever gets the higher roll gets to go first.

So, "roll for initiative" can be used as an (intentionally nerdy) synonym for "initiate a fight".

"You look like a bitch"
"Don't make me roll for initiative, motherfucker"

roll for initiative by DC-R July 26, 2016