The damage to your rose buds sounds like an insect problem, possibly thrips. Rose thrips and other thrips species lay eggs in the rose bud where the young will be protected. The insects pierce the flower petals, sucking out the fluids, and causing brown discoloration. These articles about thrips in roses from The Indianapolis Rose Society, the Master Gardener Association of San Diego and North Carolina State University Extension include photos to help you identify your problem.

Rose buds in early stages can also be damaged by weather, so if you have had recent cold, wet or very humid conditions, that is a possibility. Once the rose bud begins to open, moisture collecting on the vulnerable new petals and not drying off quickly, can cause petals to rot.

I suggest that you explore a damaged rose bud for the presence of tiny, yellow insects (thrips can also be darker in color) by cutting into it and tapping it upside down onto a sheet of white paper. If you discover thrips, you can contact your county's cooperative extension office for information on the management approaches that are licensed and effective in your area.

You can read about other common rose pests and diseases in our Guide to Rose Problems.

Courtesy of NYBG Plant Information Service