stems on several roses turning brown and dying
Stems are dying back to the main branch - sometimes the main branch is dying also. All of the plants bloomed well in the spring.
This sounds like either a boring insect has bored into the canes, they have sustained some sort of injurty or something has been poured onto the soils that is killing the root system. Neighborhood dogs or coyotes peeing on the rosebushes or around them will cause this as well. This will require some further investigation on your part. Even a late in the evening visit to the garden areas with a flashlight is a good idea. I would prune out the bad and dying parts, then water the rosebushes with some water that has a product called Super Thrive and a good root stimulator mixed into the water. Do this the next 4 to 5 times the roses need watering. It will help with any stresses or shock the roses are going through. You might also water the rosebushes once real heavily first as this will help flush out/dilute any animal urine that could be causing the problems.