There are four main categories of when one would say, "roast on you."
1) they are flirting or be flirted with
2) somebody just told them off, they got burned, or they just said something stupid
3) they burned some one else
4) something amazing or extremely hilarious just happened
When You roast someone like a muffin it means you roast them Like a white person. (White People can't roast, Besides I'm White, I know what it's Like).
