if the prospect is preemptively cleared by the ncaa after an investigation, then the school should not be punished (at least not by probation) for allowing him to play. in the cases of most prospects, they are not investigated thoroughly before playing, so the school should be punished for not taking the necessary steps.
in sidney's case, the NCAA is doing a thorough preemptive investigation into his amateur status. if he is cleared by the NCAA, it shouldn't matter if new evidence comes to light in a few years, unless the school knew about it and covered it up. i don't know if rose's issue was initially investigated by the NCAA, but if it was, and they said it was okay, then the school shouldn't be punished now. sure, you can call their wins from that season "forfeited" because they were playing with an ineligible player. but if the investigation was led by the NCAA, the school shouldn't be punished for relying on that investigation.
of course, though, i know that this is the NCAA, and nothing they do really makes sense anyway.