well, I think they are all flammable, but most especially the spray foam. The "skinned" foam boards may be slightly more fire resistant, but I wouldn't put too much faith in it.
I found the real rock wool insulation to be superior for me. It's green colored. You can put a propane torch to it, and it MIGHT barely singe. It can be a bit tough to work with. I bought it in batts, and bought several cheap(disposable) electric carving knives for cutting it. Unlike fiberglass insulation, it's unaffected by moisture.
