Yes, the T1 Line is run throughout your dorm, then you don't need a T1 Router or anything. This is most likely how it's laid out...
1_ T1 Connection To Dorm
2_ T1 Router
3_ Network Switch(es)
4_ Cat5 cable run to each of the dorm rooms
5_
Your Router
6_ Everything behind your router
You can use any of the major brands of personal routers. Just make sure that if you use wireless, you encrypt your signal, as people in dorms tend to use other peoples internet connection so they dont have to pay for their own. Here are a few links to routers you might be interested in.
LinksysWiredWirelessD-LinkWiredWirelessNetGearWiredWireless
Hope this helps!