Thanks for writing. There are a number of pests that will eat rose leaves. I'm sorry to say that without being able to see your plant, I can't tell you exactly which pest you have. It could be deer or rabbits, slugs or snails, beetles, or caterpillars.
Take a look around your plants and see if you can determine which pest it is. If it's caterpillars, you can try hand-picking them or spraying with insecticidal soap. If it's beetles, you may hand-pick or spray with neem oil. If it's deer or rabbits, you may need to fence or try an animal repellent.
---Justin, Senior Garden Editor, BHG.com