I disagree. The roast wasn't actually at all disrespectful, but that's not the point, my humorless friend above notwithstanding.
IMHO, the President of the United States gets far too much respect, for a democracy with no royalty and no classes. George Washington would be embarrassed.
It is the very instinct to treat our leaders as if they were royalty -- to think that because the "office" of POTUS is so (excessively) powerful in domestic and international affairs--that somehow the holder of that office personally deserves to be treated with -- not just respect, but deference -- exactly this misguided instinct that risks turning a nice, grounded guy like Barack Obama into another George Bush II.
This country really needs a guy to walk beside the President and mutters in his ear while others sing hosannas, "Remember, Caesar, thou art human!"
The President should be addressed as Mr Obama in regular speech among his colleagues, not as Mr President; so likewise Senators, who get swelled heads from being called Mr or Madam Senator. G. Washington hated being addressed as Mr President, but settled on it rather than having to hear "Your Excellency." His distaste for titles -- and for the instinct to genuflect before power -- was well founded; too bad it has long been lost.
When a comedian can't make a disrespectful joke about those in power, power has gone too far.
[By the way, John Hodgman's Roast is hilarious, gently humorous, and reveals Hodgman, the "I am a PC" actor in the TV commercial, as a real wit. Worth viewing. Hodgson is a humor writer with a great bio on Wikipedia.]