Bitch slap your roommate and take a chill pill. Do NOT respond to the copyright holders (MPAA / RIAA / etc) directly. At this point in time, they don't know who you are, they just have an IP address. The only one that can tell them who's under that IP addy is your ISP. They usually won't give that up without a court order, as "policing the internet" is not in their job description.
If your situation is at the point where your ISP is calling you (usually it's just email forwards), assure them that you've figured out the problem and have corrected it. Usually the worst case scenario is that your ISP may drop you for being a repeat offender (for being a pain in their ass). But usually they value the money they get from you. I haven't read of a single case of this sort of thing going to court. So calm down and take other people's advice in this thread. Make sure you tell your roommate that although he's listed under the IP address with YOUR name, he is equally responsible for what's downloaded at your place and you WILL give him up.
If your situation is at the point where your ISP is calling you (usually it's just email forwards), assure them that you've figured out the problem and have corrected it. Usually the worst case scenario is that your ISP may drop you for being a repeat offender (for being a pain in their ass). But usually they value the money they get from you. I haven't read of a single case of this sort of thing going to court. So calm down and take other people's advice in this thread. Make sure you tell your roommate that although he's listed under the IP address with YOUR name, he is equally responsible for what's downloaded at your place and you WILL give him up.