This kind of question always comes up when something like this happens... just hasn't happened of this magnitude since Pierre Pierce.
We can really be thankful that we have a character coaching staff, and a lot of character young men in this program. Incidents like this always illuminate the offender brightly and cast a shadow on everybody around them. This would include everybody in the program. I expect that this football program will deal with this incident in a correct way, and come through stronger for it.
That being said, I teach in a performance medium, and have had students arrested for similar infractions. In my experience, there was no knowledge of the individuals dealings by teachers or peers, although we knew there was a problem of some kind. I would suspect a similar situation was true with the Iowa football program, although there were rumors a plenty in town, and it seems unrealistic that some of the players did not know or even participate. It is best to allow the "onion" to peel naturally in this case, and watch Gary Barta and Kirk Ferentz do their jobs (who's complaining about salaries, now?). It's lucky this team did well enough to qualify for a bowl game, to allow the program the time to weed through this incident while still "in season".