Justina Valentine Roasts Nick Cannon on 'TMZ After Dark'

"Wild 'N Out" star Justina Valentine hijacked "TMZ After Dark" over the weekend ... and she didn't just prove she's a freestyle beast ... she also made sure Nick Cannon caught a few hilarious strays along the way!

The shots at Nick weren't random either ... considering it was Mother's Day weekend, Justina wasted no time clowning her boss the second she hopped on the bus -- joking the holiday was basically Nick’s Super Bowl.

Justina REALLY sent the party into meltdown mode when she compared Nick to Oprah Winfrey ... except instead of giving away cars, she joked he's handing out kids. "You get a kid! You get a kid! YOU get a kid!!!" ... and yeah, the whole bus lost it!

Beyond the jokes, Justina reminded everybody she's a legit freestyle assassin ... roasting passengers left and right while DJ Blue kept the beats coming nonstop, as the Hollywood bar crawl kicked off at The Burgundy Room, before the crew rolled over to Beaches Weho.

Shots were flowing, bars were flying, and by the end of the night it was pretty clear ... Mother absolutely delivered on Mother's Day weekend!