A few things come to mind. 1. Leaf scorch from reflected sunlight hitting the foliage that acts like a magnifying glass on the foliage. 2. A local dog or cat is relieving themselves upon the roses foliage causing foliage burn. 3. Over-spray from an herbicide drifting over onto the roses foliage. 4. Insecticide spray that has either been mixed a bit too heavy or has stayed upon the foliage too long due to cloudy weather, thus burning the foliage. 5. Last and the least likely, the rosebushes have not been getting enough water and are letting leaves die in order to preserve its life as best it can. Now you will need to investigate and see if any of these items fit your situation. Let me know if I can be of further help. Here is an article for you to check out as well: https://www.gardeningknowhow.com/ornamental/flowers/roses/brown-edges-on-rose-leaves.htm
Stan The Rose Man :)
