After the beetles have eaten about half the rose leaves and have been killed by Sevin spray, should the bushes be trimmed back or what?
Caring for Knockout Roses Damaged by Japanese Beetles
Leave them alone for a while and see where the new growth comes in at. Then you can prune back as needed to re-shape the rosebushes. Pruning them back now would add more stress to them and would also probably be far more pruning than is needed. If you can find a product called Super Thrive where you are, mix a tablespoon or two of that with some root stimulator in a big watering can. Water the rosebushes with that mix a couple times about 10 days apart. It helps with shock and stress.