Hi,
What size rats are these?
Because if you leave them in the water till they are defrosted completely then at that point i'd get the hairdrier going and feed them to the snake.
I can defrost a jumbo adult mouse using a heatmat from hard frozen to ready to air blast in three hours - a small rat takes maybe 4 or 5 tops.
But I would let your nose be your guide - if it really stinks I'd wave it at the vendor asking if he would eat that in an outraged tone.
dr del