Yes, you should go get Roger Clemens for your fantasy team.
There, I've just headed off your e-mail and chat questions about the hefty soon-to-be 45-year-old. He's eminently usable in fantasy baseball. He'll get 18-ish starts if he joins the Yankees on June 1; he'll probably give you an ERA of about 4.00; and he'll post strikeouts. Plus, he'll win between eight and 10 games.
But let's look at the other end of the spectrum. Maybe Clemens is gone in your league. It's notable that on a day when Yankee radio announcer Suzyn Waldman nearly had a heart attack breathlessly heralding the Clemens signing, a young man named Tim Lincecum made his debut for the Giants. Talk about polar opposites. In a month, Clemens will enter his 24th season for a scant $28 million prorated; Lincecum is about to turn 23 and makes the minimum (although he did get a $2 million signing bonus last year). That's right: Lincecum wasn't born when Clemens made his big league debut.