Exceeded Profile Storage Space

We set up roaming drives for each of the teachers here in this facility yesterday so that they could access files no matter which computer they logged in to. Some of the teachers now receive an error message stating that they have exceeded their profile storage space. All of my research thus far has indicated that they have more files being stored in there than the allowed limit is but the problem is that we did not set a limit on the amount of data that could be stored. The other problem with that theory is that there is nothing in their personal drive on the network yet. Like I said, not all teachers are having this problem, in fact, most are having no problems at all. Any help on this matter would be greatly appreciated. Thank you.