Thanks folks. I was thinking that is what I should do, but was needing some confirmation.

I've got scads of nursery pots and the local transfer station also has a recycle shed just for nursery pots that the folks who grow for market cycle through, so hopefully I won't have to buy much other than some big pots for the peonies. I've already put pots under the roses and hydrangeas and pegged branches to start rooting.