freeze chicken carcass?

yes

If it is roasted you just break it in half and put in a quart ziploc bag and freeze. If that takes up too much room in your freezer you need to move out of the dorm.

You can leave for a couple months or so and just add more bones to it. Freeze any old wilted vegetables you have as well and use them to make your stock. Go to Wal Mart and buy a few plastic ice trays and when your stock has cooled, skim the fat off the top and put the stock in the ice trays. Freeze then pop out and put in ziploc baggy.