Brown leaves on knockout roses
Any more information you can provide would be helpful. Have any herbicides been used in the area? Any equipment that could have had its exhaust directed toward the roses? Have any fertilizers been used on the roses? There is what looks like new growth at the tips of some canes and some of the canes are green. But the leaves are brown, and there are flower buds never opened,
There has been no fertilizing or exhaust. Just planted, mulched and left alone. The winter was especially brutal and spring very wet but soil drains nicely.
Judging by the photos it looks like the plants leafed out and there was growth til around the time that the flower buds developed. There are flowers that did not open but the buds were formed and the flowers were developing. Based solely on what is visible in these pictures, it does not look like an insect or disease to me- it looks like something related to a chemical, heat or weather, i.e. freeze damage. Without seeing the roses, or samples, I am not sure what caused it. At this point, I suggest you cut off any dead canes and leaves back to live, green wood to see if they will regrow. Wait until the plants are dry before doing any pruning.