Hello, and welcome to the forum! It would be best to store the roots in barely damp peat moss (about 1 cup of water per cubic foot of peat moss) and keep them cool - here that is accomplished by keeping them in the unheated garage in early fall, but zone 7 is a lot warmer than where I am. If they are too warm they will rot.
After learning the hard way I'm of the opinion that peonies aren't really fit to be grown in pots, but with that said, I have seen folks that have been more successful with it than I. Hopefully they will chime in with some advice. Good luck and enjoy!
