Lampanelli -- Joan Rivers Roast Wasn't Worth It

There's a reason insult master Lisa Lampanelli didn't show up to the Comedy Central roast of Joan Rivers this weekend -- if she couldn't be in charge, it wasn't worth her precious time.

A week after Kathy Griffin was announced as the roastmaster for the event in Los Angeles, Lampanelli -- who's usually the headliner at these things -- dropped the following message on her Twitter page:

"No Joan Rivers roast for me this year. Not worth doing if I ain't roastmaster -- besides summer is for fun, not work."