The first thing I would do is pull the mulch back from the base of your roses. It may not be a problem yet but it does cause rose cane problems. Then hurry and water that rose if you have not already done so. There is of course the possibility that the water is not draining well in that spot. That is something you can check by digging down a bit. Either problem can cause the leaves to brown so it is important to check. Be sure to check the other rose as well to see how its soil is to give you an idea of why it is happy. Then with a gloved hand check to see how solid the rose is sitting in the ground compared to the other rose. The canes are still green so she will leaf back out once the problems are solved.

Sometimes it is as simple as air pockets. For this you can step on the soil around the rose a bit to firm it up.

I'll stop here as to me any way it looks like a soil water issue. I would also give the rose some shade while it recovers. Leave the leaves on for now so they can also help shade the canes. Try to remember to pull the mulch back from the canes. Good luck with your rose baby.

Good point that Jim brought up about fertilizer. That is also a possibility. It is important not to fertilize a stressed plant. Any chance this one had more fertilizer than the other one?

Check your sprinkler system, the emitter near that plant may be clogged. Also, move the plant to see if it is firmly in the ground. Something could have disturbed the roots.

I think we've covered about everything. No way anyone is tossing anything out of the window?

It's also below a window. The glass could be reflecting more sun and heat than the plain brick does.

Thanks everyone for the input! I went and pulled the mulch back on all the roses and I found some air pockets in the soil underneath in the one that died, the sick one and another that was still looking healthy. I've filled them in with some garden soil. I had fertilized them last week (for the first time this summer- I know it's been busy) so that may have contributed. I won't fertilize again this year! I also made sure to clean out any dead leaves from underneath and I removed any leaves that looked like they may have spots but left the others to provide some shade to the canes. Hopefully it comes back, if not hopefully I at least prevented the other three from getting sick.

Best of luck selint387! I hope you get things figured out..

Remember your rose is not dead as long as the canes are green. Do you have a lawn chair or something to give some shade while it recovers? Your rose will thank you.

I do have a chair I can put out there. It's pretty gray and rainy today but when the sun comes back I'll give it a little extra shade.