Like lori said, foil. However, I never carry foil or pans and like to roast bass/trout/bluegill/crappie using a skewer or twig grate. The skewer thing came from my Boy Scout days and they are still teaching it. No seasoning at all. I like to use a bigger stick than the article below shows.

http://boyslife.org/outdoors/outdoorarticles/2737/scout-program-cooking/