Since it's concurrent with recent fertilizing, my first bet is fertilizer burn. Also the very high temps.

If you can gently remove any remaining fertilizer, do so. Since fertilizers are salts, keep the plant well hydrated, but not soggy, & you might even throw shade cloth, a sheet, an umbrella, or some branches over it to mitigate the high temps.

When you live in a hot area (been there all my life), stop any major fertilizing June-August--they just can't take it. Hybrid teas & many other roses may even totally defoliate & essentially go dormant during that time of year. Let them rest--they'll leaf out & give you a good flush of blooms starting in Sept & continuing until frost or even through winter.

You might lose the rose--I still occasionally kill one trying to *help* it with fertilizer when it's just TOO DANG HOT!!!!--but keep it well watered & shaded a bit & maybe it will pull through.

Severe leaf burn usually means the leaves have been unable to supply themselves with water--or sometimes they are burned by a foreign substance such as foliar feed or pesticide.

Causes might include--

-Arizona sun, heat, and low humidity
-new plant had root ball disturbed during transplanting
-not watered enough
-excessive fertilizer'
-sprays such as neem oil

Water thoroughly and give partial shade.

Remove anything that looks dead and water, Water, WATER it. If it's lack of water that will help. If it's over fertilization the water will help flush it out. It it's the heat water will help. In any case it needs more water. And as Michael said, shade it some way during the worst heat of the day. Put a lawn chair over it if it's not too tall or make some kind of awning over it with cloth and stakes if possible.

Check around the base of the plant to make sure there isn't a handful of fertilizer touching any of the canes or shank. A "glop" of fertilizer pellets against the plant will burn the devil out of it. If there is, remove it and as much of the soil under the "glop", replacing with clean soil which isn't saturated with fertilizer, then WATER like a fiend to dissolve and flush through as much of the fertilizer as possible. All the other suggestions are great, just add this one to them to cover pretty much all the bases and good luck! Kim