Purchased a raspberry sundae peony last year & it looks like it didn't survive the unusually wet garden we had this year. When I dug it up, it did have some root hairs at the bottom still. Can I salvage it by cutting off all the the rotted parts & potting it with good drainage soil with rooting hormone? Should I spray with fungicide? I'll obviously have to find a drier spot for it if it survives the potting.

It won't hurt to try. Don't put the pot in the full sun as the heat plus not having leaves to shade the root may lead to rot.

Good chance. Cut off the rotten part and plant the rest. It has worked for me sometimes.

Nate does not recommend pots for peonies. They had a flooding summer one year and had to replant the whole field. They cut off all rotted roots, dipped in 10% bleach and planted in soil. Good luck!