"You know how you can look at a person and, like, they're trying to have a good time, but you can tell there's a tear... There was one moment when I looked at Justin and he was like... it was like a laugh but it's not. I kept pointing at him like, 'You better hold it back, boy...' He did one knee slap, where I think he covered up a cry... It got a little rough." Justin Bieber's 21st birthday roast, which was taped for a TV special at the weekend (14Mar15), was tough in places, according to host Kevin Hart.