Wow - something dramatic happened. My best guess is they were hit with an herbicide or a rodent destroyed the roots then a heat wave scorched the tops to cause such a  quick decline. No insect or disease problem would move this quickly. If you live in a hot climate and the roses are new they could have dried out.  If you had an unusual late frost then it is possible the new growth was frozen by a sudden cold spell. I would cut the rose bushes to the ground just below where they turn brown. If new growth pops up you may get a second chance. Most likely you will have to dig them out and see if there is any root damage. If not talk to anyone that sprays herbicides in your neighborhood and see if your roses were accidentally sprayed.  Perhaps someone thought they were spraying a disease or insect spray but used the wrong product. We all learn from our mistakes when it come to gardening so don't give up. Keep growing, Marianne Binetti