Another strategy -- requires some care -- is to do what I used to do
when I messed up a pan when camping. Put it on the stove. Put in
enough water to cover the bottom. Add a little detergent. Heat to
boiling. NOT so high you boil it over. Boil for 5-10 minutes -- you
have to regulate the heat carefully. Then carry it CAREFULLY to the
sink and work the loosened crud off with a plastic scrubber.

Again, as another poster points out, it might be just easier to chuck
it. For one-shot roasting projects, there are those nice heavy foil
pans you can get in the supermarket. Best deal ever for the annual
turkey roast, which is a real PITA to clean up.