Yes, Rosie O'Donnell is ''talking to an unidentified television network about a possible show. They told me not to mention this show, so I'm not mentioning it.'' But the erstwhile View moderator who is referring to reports that MSNBC is courting her for a prime-time program had plenty to say on other topics as she opened the New York Comedy Festival at Lincoln Center on Nov. 6. The full house was rewarded with riffs on everything from O'Donnell's sympathy for Britney Spears (''I want her to come live with me, but I have to stop saying that; I'm a 45-year-old lesbian'') to her hatred for President Bush. And in case you're wondering (of course you are), there were only a few dismissive View references (''It's over, so don't ask''). The audience also got a surprise visitor: Roseanne Barr joined O'Donnell on stage and joked, ''I know you're saying, 'What has a has-been of your magnitude been up to?''' (Her answer: performing on gay cruises.) The two capped the night with a foulmouthed duet of ''I Got You Babe.'' ''I've always wanted to do a variety show with you,'' O'Donnell told Barr. Now, there's an idea for MSNBC.