I would not fertilize them just give them plenty of time to recover. Not sure which planting zone you live in, but own root roses are hardy here in zone 4. I have some own root roses that have been here for years, some winters the rabbits damage them, after they start showing new growth I prune the damaged canes back. Be patient and when the roses have plenty of new growth you could fertilize them lightly with fish emulsion which roses love.
Welcome to NGA!