I believe your roses have botrytis blight. Cutting off infected buds is one way of dealing with it. The spores are easily spread, so seal them in a plastic bag. Also be sure to wipe the blades of your pruners with alcohol after every cut. To much nitrogen fertilizer encourages it. So does overhead watering. A fungicide called Soap-Shield is the kindest to the environment. It's available on Amazon. Best And Happy Yardening, Nancy.