Ahhh...ok this may not be the sun. what color is the rose. Red, probably the sun. A pastel color, white/pink it could be thrips. To get rid of that use Bayer for flowers, it has merit in it, that is the only thing that will kill the thrips. Personally, I just let the thrips live, I hate using pesticides, and generally the green lace wing bugs and the birds will take care of the thrips for me.

alan