A justification for how someone behaves
Brendan: Hey Rob, why are you at a 20% in science?
Rob: Because I don't hand in any homework
Rob: Because that's how I roll.
used to affirm one's impressive attribute
-you always carry around $5000 in cash?
-yeah, that's how i roll
-did you just kick that guy's ass because he looked at your girl?
-you know, that's how i roll
A completely arbitrary and pathetic way to excuse any sort of behavior. By defining an action or ideal as "how you roll", you make whatever you're describing perfectly acceptable to any and all audiences. After all, it's how you roll.
Girl: Hey, what's wrong with you, grabbing a stranger's boobs in public?
Guy: Sorry, it's just how I roll.
Girl: Okay, that's fine then.