quests for rusty about Grandma
Freezing rats is not an effective method of killing internal parasites. Becky actually covered this in the "My theory" thread very eloquently. She is taking a parasitology class and the words are from the mouth of her professor (a DVM).
Now I'm sure it would kill external parasites, but if your rodents come with snake mites, don't freeze them, find a new rodent supplier.
-adam