This has been working for me:

Put the rodents into a sealed bag, squeezing out as much air as possible.
Put them in the bottom of a large coffee cup.
Use a butter knife to weigh them to the bottom.
Fill the cup with the hottest water I can get out of my tap.
Let them thaw for 15 minutes.
Pull out the largest and check behind the head and at the widest part of the thighs for still frozen bits. If still cold I start over again.
If nice and warm I offer them up.
A minute or two back in the bag/cup will re-warm a rodent for a slow to grab snake.