Usually I've seen people either toss those to another snake (like a BP who will take it as a lil snack) or toss in general. Reheating gets more dangerous the tinier they are and makes them more prone to pinky glitter explosions, lol.
For OP: My usual method is "thaw in hot water, remove, blow dry til dry, heat head warm to touch" so the rats are rarely out over an hour. If your heating method requires they are out over an hour, I'd say toss them. Eventually, you'll be able to judge what seems safe for a refreeze based on body feel, smell, etc. Just takes some time and practice to be able to figure it out. NBD.