Sharing ports violates official university policies regarding computing resources. Each port is for the sole use of the person who registers it and pays for it—use by anyone else constitutes theft. Therefore, you and your roommate may not share a single port.
Be aware that whomever registers and pays for the port is completely responsible for ALL activity that occurs on that port. This includes any illegal acts perpetrated by anyone who has access to your port, even if only for a few minutes. Therefore, you should not let other people use your port for any reason. Refer to the Acceptable Use Policy for more information.