The easiest way (not the cheapest) is to let a lawyer do it for you. Get a landlord tenant lawyer. The less expensive but more difficult way is to go to the local landlord tenant court (probably in Rome NY City Court) and file the action yourself. If you are nice about it a clerk may tell you how to get the summons and complaint served.
Finally, DO NOT THROW HIS STUFF ON THE STREET. You could get in a lot of trouble. Next time if you think you may not want a roommate, don't take any money. It gives the roomie rights.