If you had an agreement, even if only an oral (unwritten) one, that you and your roommates would share the cost of the utilities, then if you were credited more than you proportionately should have been, or they had to pay more than they proportionately should have paid, under the terms of that agreement, they could sue you to get their share of the money. If you are in another state, they might not bother doing so, since suing cross-state is more difficult and expensive--but legally, they could sue if they chose, based on your agreement regarding utilities.