To me it just looks heat stressed. I have sunburned canes here and older canes that look like yours and I think the roses will grow new healthier canes and these old canes ultimately can be removed. I just try to give plenty of water. Some shade their roses with an outdoor chair or sun cloth in the heat, and I'm sure that can help. I do not know the name of your rose.

It’s also possible that the white on the canes is scale.

You also have reflected heat from the wall behind it. Makes it even hotter. As Sheila said, some temporary shade would reduce stress until it cools off in October.