If you bought a live one and wacked it yourself, go for it depending on how long you left it in there. I'd be warry of freezing a rat that was left in overnight ( dont know how fast decomposure sets in ). If it was f/t, same thing. I wouldn't refreeze it more than once tho. I've heard horror stories of exploding rats, besides that the dead rodent probably cant take too many drastic changes in temperature while still staying "fresh".