It sounds like botrytis blight. It is a fungal disease that goes after light colored blossoms. I figure that it is still cool in the evenings in Indiana. I understand that botrytis blight likes it cool and damp. Your rose should be better in the summer. I have a number of roses that can get hammered by this disease under the right conditions. Clear the infected blooms and throw them away. Goggle botrytis blight and learn more. Knowledge is our friend. If you feel that you have to do something, get some fungicide that is copper based. Now this is not something to over use. Too much copper is toxic to all living things, but if you follow the label to the letter it will work. Since I haven't seen a photo of the plant, I am just giving a guess as to the problem though. I love reference books to look things up and there are many good rose books that cover rose afflictions. Ironically, I find that it can be very difficult at times to find thins on the web. Let me know what you find out.