To harm someone physically and mentally because whoever is roasting and or being roasted is an asshole. To roast in a group of people is known as a "Squad roast". And you will be known as the assholes of the school, work, or wherever you go to waste your life.
The fattest bitch in my school pushed me out of the way while screaming "Move fat-ass!" And boy did shit go down because that night she received a roast from my squad. - Russian Soviet 2004 or some bullshit
I guess people from the south say this when there about to insult someone profusely. If you ask me, on the north side, we don't say roast, we say barbecue.
Look at those shoes Janie got on, dang she better not say anything to me or else I will roast her ass!
Helen roasted Uranka so bad, he almost made her cry.
J: Look at those two-toned shoes D got on
D: I kno u anit talking with that shirt. It streches so far that u dont even have to iron, EVER!!
Everybody: ROAST!!!!