I would lay them out individually on a disposable or old cookie sheet and let them start to freeze (a proper freezer rather than a fridge top one would be best). Once they have started to freeze individually and are therefore less likely to freeze in a clump of rodents, I'd put them into a freezer grade bag and use the product listed below to remove all the air (you can buy the bags that come with this in two sizes).
http://www.reynoldspkg.com/reynoldsk...ac/en/home.asp
This product sells for under $10.00 and the bags are reusable. The nice thing is when you are feeding each week you could remove whatever number of prey you need and very quickly get the bag back into the freezer with the air removed efficiently.
One little trick with bigger rodents is to lay them belly to belly or back to belly so that their claws are turned inward to another frozen prey item in the bag so when you draw out the air you won't create a possible puncture of the freezer bag.
I own one of these and find it does a great job for the price point.![]()