nope. if it's funny then it's funny, fuck timing. gilbert gottfried and george carlin and other great comedians never worried about offending their fans or detractors. if they don't get the joke and the context it's in, then fuck 'em.
I cringe at roasting when it involves me. I never have a comeback and when I do, it's usually terrible. Not cringing at the jokes, i'll just be scared because I never know what to say.
Another thing I cringe at is if the comedian ignorantly believes in negative stereotypes of other people. It's okay if you know it's not true and you're making fun of the stereotypes themselves, but when you sincerely believe in them it's a different story. Like a real racist telling a racist joke and thinking it's true.
And uh... timing doesn't matter to me unless I'm a victim or know a victim affected by the event you joke about. I know that's bad but it's true. I have no emotional ties to the joke so I'll most likely laugh it off.