The last joke isn't even funny and it's more offensive and tacky than anything.
Regardless of that, my real issue is why must the comedian insult Selena in a JUSTIN BIEBER roast? It seems cowardly to sling a woman's name in, throw her through the mud to insult a man. That's truly repulsive. If that's "comedy" then, insulting people must be like murdering people now.
If you want to insult Bieber for a roast then roast him. Selena's name shouldn't have been mentioned. There's way more moments from Justin's career to lash him with...like an infinite amount.