Old rambler roses should be pruned immediately after flowering. Leaves are eaten off my rose bush. Sometimes the whole leaf blade is gone, and other times, the leaf is half eaten. Probably some type of chewing insect. Examine plants frequently to see if any pests can be found.
Treatment depends on insect.
Leaf cutting bees or ants are a common problem. Pickle juice would be acid, so it would lower the pH somewhat, but sulfur would be a better choice. You would need to know the actual pH before you did anything. Roses can be started from terminal cuttings or leaf bud cuttings. However, because all hybrid roses are grafted onto a common root stock you should buy the variety you want that is already grafted.