Looks sunburnt to me. We had that heat wave right when everything had pushed out a lot of tender new foliage--the plants couldn't take it. I think your plant will be okay there, but I'd rig up some temporary shade to get it through our next heat wave due Tues-Friday.

They could be any number of caterpiller, larvae, etc... without pics and more info it would be difficult to make an exact ID. I simply pinch them between my fingers when I find them. They are probably some type of sawfly larvae, at least that is what I get here. The ones I typically get are green with whitish spots down the length of their body. Sawflies are a small non-stinging type of wasp. Adult sawflies are not a problem, but the larvae are. Sawfly larvae are also called Roseslugs. They feed from May to September for 2-3 weeks when they are in larval stage, and then they change into adult flies and the feeding stops. The reason they are called roseslugs because of their slug-like appearance. The larvae also resemble caterpillars, but they are not true caterpillars. There are several types of sawflies that attack roses as larvae. The bristly roseslug is a major pest on roses. The larvae are pale green, with a brownish-orange head and very small, bristlelike hairs. They skeletonize the leaf from the underside when small, and then chew holes through the leaf as they enlarge. The curled rose sawfly occurs in lesser numbers, but each one can cause relatively substantial damage. The curled rose sawfly larvae skeletonize leaves when small and eat the whole leaf, except the main vein, when large. To make matters worse, when they pupate they bore into the pith of twigs, killing portions of the twig and opening it up for fungal infections. The larva has a yellowish head with black eye spots, and a pastel green body with white dots down the length of it. The roseslug is the third type of sawfly to occur on roses. It looks somewhat similar to the bristly roseslug, but lacks the hairs. It skeletonizes the upper surface of a leaf. Easiest way to treat them, is to mechanically pluck them off and squish them. If the damage is widespread across many rose bushes in your garden and a lot of damage is being sustained, chemical control should be considered. Just about any contact insecticide labeled for use on roses will kill the roseslugs. Try to use the least toxic one possible, because you don't want to kill beneficial insects in your garden.

Turn the leaves over look close (use a magnifying glass) there may be spider mites sucking on them. They are very tiny the size of a pin head. If that's the case, blast the undersides of the leaves with a forcefull stream of water, or use a miticide.

I also think it looks like canker. The organisms that cause canker are around all the time and enter through the "skin" of a plant when it is injured, cold can cause injury so that spring is a common time to see canker damage. If the canker encircles the stem, all nutrients are cut off and the stem above the canker dies. If the canker does not encircles the stem, then it should recover. I agree that pith will show if the stem is alive or not, but you must cut off the stem off to see the pith, it is that corky stuff in the middle of a stem, but now the cane is dead for sure. You can check for life under the bark with the scratch test, and as long as there is green under the brown, there is hope. It can be false hope because the stem could have died below where you scraped and the top of the stem as yet to die, that's why a stem can continue to produce foliage for a short time even after it is dead lower down. In my experience, you can kill a weak plant by pruning off all the canker damaged stems, when if you just left it alone, it be would be ok. You can always prune the stem later if it dies, If it is a vigorous plant then pruning it won't hurt, do clean your cutters after each cut. You do not want to spread it to healthy wood.