WisBadger,
In attempt to offer you some sort of resolution, although I'm not too up too speed on the laws and/or regulations of Wisconsin, I can almost assure you that any relief that you receive from this will most likely come at the hands of your landlord.
Typically, events such as these are reversed and as opposed to it being 3 - 1, it's normally 1 - 3. Having said that I'm doubting that it would work for you all to take refuge in locating another person to fill the 4th person's void, due to laws requiring that person to physically sign themselves off of the lease agreement that binds you all currently.
Although your University has viewed the e-mail printouts, chances remain slim to none that this is going to veto your unwanted roommate from the lease without some sort of proof that their is negligence in his/her paying the rent in a time efficient manner, etc. Translation: No one is going to "get the boot" merely because you all can't see eye to eye on things.
If anything, you should contact your landlord, warden or whomever is deemed as being responsible for situations such as these, and might I recommend that in the future you (and your roommates) consider researching one's behavior patterns a bit more efficiently before signing any sort of legally proficient documentation as to prevent any more occurrences of this sort?

