Perhaps people don't understand the purpose of a roast. They're supposed to be wholly inappropriate. Maybe they're not supposed to be on TV. The "so-and-so ****s so many black guys" jokes and cursing and sexual content have become cliche and commonplace.
Kimmel's joke about Chris Benoit was the only one that made me cringe at the inappropriateness, and therefore about the only joke worthy of a roast. Again, these shouldn't be on TV, but the whole point of them is to be inappropriate.
Flav's joke on Snoop "it's not the first time you've gotten away with murder" was also a good one.