Roger probably plans on retiring right now. But he shouldn't. In fact, he should attempt to return at whatever salary for whatever team for one reason: to force Bud Selig to attempt to suspend him.
If Selig chooses not to try to suspend Clemens, Clemens can use this as public talking point #1 that he is not guilty of PED use. If Selig does try to suspend Clemens on the basis of the Mitchell Report, Selig will be forced to fight the players' union. The players' union will drag lawyer after lawyer after lawyer in front of an arbitrator, each saying that the evidence against Clemens is highly suspect and does not warrant a suspension. Clemens would almost assuredly win that fight, giving him public talking point #1 that he is not guilty of PED use.
Plus, he would do this while not being suspended for drugs while he's playing yet another year. Remember, much of Clemens' late career dominance came while MLB had drug testing. If he plays in the National League, he'd probably put up very good numbers, further bolstering his case. He can even make a public show of his lack of positive test.
What does he have to lose?