Favorites so far were the Sagat Roast, the UK Roast of Sharon Osbourne, the Shatner Roast (Takei destroyed him) the Charlie Sheen Roast. Some were just terrible: Trump Roast (The Situation? Really?), The Pamela Roast (Do more jokes about her boobs being fake!), the Flavor Flav Roast (They weren't even B List comedians at that one), the Joan River's Roast (Practically slept through it).
The consistant Roasters they have are just boring as all hell. Even the Roast Master fails more than he makes a laugh. I usually find myself more entertained by the guest Roasters (Takei, Gottfried, McDonald etc).
Some favorite clips: