Is there anyway to know if someone is torrenting in my network?

Just block all ports on the router except for http and maple port (dunno what is is though), and wait for someone to start complaining!

I live in a dorm.

The entire building shares the same connection more than likely. His personal router is irrelevant to what everyone else is doing, since the implication here isn't his own room as the culprit.
Having access to the building's, or even the floor's is unlikely.