No, that's not sun scald. That leaf pattern is common to water stress in roses.
Now, don't jump on me and say that your roses were never water stressed. On any rose in hot weather even half an hour of water stress can cause a few leaves to show that pattern. It's no big deal unless the whole plant is showing that symptom of water stress.
Roses often will abandon leaves in order to survive in the heat. They will use all available moisture to keep the root mass alive and not send moisture up to the top growth. It's how they are genetically programmed to survive.
With our drought and often with water restrictions, many rose gardeners are finding this in their gardens. I've even got a few roses that are the more thirsty roses than the others screaming at me to water them more in my triple digit temps by showing this symptom on some of their leaves.
Smiles,
Lyn
