For what its worth … I think there should be an independent investigation into this.
Not one run by NDSU, one run by and headed by someone not beholden to NDSU (or the Robbins-es) and whose assignment is to get to the truth - as much as that might be possible (given that people will lie to cover their behind, or the ones who feed them).

By now, however, one could probably expect that the people who are worried have already taken steps to cover their steps, discard evidence, etc.

Other players should man up and speak out - some were there, if there is truth in what mama Robbins said. However, if they feel their scholarship (etc.) wd be at risk, they may not want to say anything. Most people will not go out on a limb and 'do the right thing' when doing so will cost them something (like a scholarship). I hate to be cynical, but …