After Junior is intimidated at school, Dre decides that physical fighting isn't the answer—verbal warfare is.
Junior succeeds a little too well; he begins roasting everyone, including his parents, causing chaos at home. The Battle for Sleep
Detailing the behind "The Dozens" referenced in the show Let me know how you'd like to continue ! "Black-ish" The Dozens (TV Episode 2015) - IMDb
Dre schools Junior in the traditional game of trading insults, specifically "yo mama" jokes and personal roasts.
Junior is being bullied, leading Dre to teach him how to "roast" opponents into submission.