The Clintons have a way of getting their pals aquited. I'm not sure how they do it, but this whole thing could backfire on the justice deptment and actually work in Hillary's favor.
There will either be an acquittal, the charges will be dropped, or David Rosen will take the fall and clam up, like the McDougals did. In any case, nothing will come of it that will hurt Hillary. Bet on that. It may in fact end up helping her, as you suggest. The lamestream, lying scumbag media will race to Hillary's defense with the tired old victim-sympathy angle ("Aw, those wasscally Weepublicans are picking on that poor wittle woman!").
David Rosen may fall on his sword and lose his freedom for a short time as a result, but he knows better than to cross the Clintons, and what happens to those who do. Better a little jail time than six feet under.