Red beans and rice freeze very well. And you can certainly freeze the beans and rice together. But I recommend doing so separately. The best way to freeze leftovers is in an airtight food storage bag using the water displacement method. Simply fill the bag with your leftovers and submerge it while it's still open in a large bowl of water. Once the water reaches the bottom of the zipper, seal it well, and lay it flat in the freezer.