Have you checked for thrips? Lots of tiny, barely visible, elongated tan insects that scurry to hide when you separate the petals. Thrips damage and Botrytis damage can be confused with each other, or can overlap.

Copper soap sprayed on the buds during cool, drippy weather can control Botrytis fairly well, but it may spot some flowers. It is also moderately hazardous, so cover up and then change your clothes if you use it.

In Texas, Botrytis should be a transient problem. Thrips are transient for me as well. If you have serious recurring problems with either, perhaps the best course is to discard the most susceptible varieties.

If the striped roses are together on one shoot, it could possibly be a valuable mutation, so preserve that wood and see if it keeps producing those blooms.

Oh, Michael, would that botrytis were only transient here!

Botrytis can be prevented (the best cure) by spraying early in the year, immediately after pruning, with lime-sulfur or Bordeax mixture. Otherwise, during the season, cut out the offending parts.

I meant transient in the course of the season, in that it isn't active in hot, dry weather. But it will be around next year. As Field implies, it can affect bark and stems in winter or early spring and cause cane losses.