Are the eaten leaves at the top of the plant or the bottom? How do the bite marks look of the eaten leaves? The spiders will not harm the rose plants. Slugs, June beetles, larvae, green worms, and tiny caterpillars all love to eat rose leaves and deer will devour roses overnight. If you send a photo of the damage I will be more accurate with a guess. Once roses bloom and then the flowers fade it is time to fertilize and water again for a second wave of blooms. You can use Osmocote on your roses in spring and again in mid summer. You may want to go out at night with a flash light and see what is eating the leaves. If you see no slugs or green worms I would suspect deer. Once you know if you have an insect you can spray with an insecticide but if deer are suspected use a deer repellent spray. Are the leaves turning yellow? You mentioned the base of the roses are still green. Yellow leaves are a sign of a disease or water issue. Don't despair, roses are tough and we can solve this problem. Keep growing, Marianne Binetti