Well, the Constitution explicitly declares that a President cannot serve more than two four year terms.
So, obviously the Roberts fix would be to rule that despite the fact that many of us have always thought of a year as 365 days, it really is 1,000 days for the balance of the Obama term.
Remember how Roberts screwed up the oath of office and had to go redo it a day or so later? He'll simply rule that because of that, Obama's first term was less than four years and thus he is eligible to run again. Simple.