Fran, you need to do some detective work, digging around in that soil. Perhaps it's compacted and the drainage isn't good. Perhaps it drains too well and the plants don't get the adequate moisture. Perhaps something which had been dumped into the soil has migrated down to the area and poisoning the rose. Digging out the area so you can examine what's under where the rose grows should tell you a lot. Usually, though, if there are issues with the ground, the problems will show up in the new growth first, but by exploring the under ground possibilities, you can potentially rule them out and place the blame on the roses instead.

Were all the roses planted there obtained from the same source? Is that end of the bed closer to a hot wall, side walk or driveway? Leaves turning brown at the bottom is normal, to a point, as those leaves are older and are used up, then their nutrients are reabsorbed into the plant to generate new growth. If that spot is hotter due to reflected, radiated heat from concrete or asphalt, it's going to need more water than the other spots. If it's a fungus or other disease, you should see evidence of mushrooms or Mycelium under the soil when you dig it out. You can then check to see if the soil appears damp, soggy or dried out and whether it smells normal or "soured".

How does the new growth of the roses look? If the new shoots remain normal looking as the plant turns brown, that's very odd. Usually, if there are issues, the new growth is going to look sick, or there just won't be any new growth. But, I honestly feel you need to excavate that spot to see what's going on under there before taking any actions to correct a problem you really don't understand yet. Might you be able to post photos of the area and how the roses look? That can often result in someone being able to diagnose the problem for you. I don't think there are too many things out there some of us haven't already experienced. Good luck! Kim

Here is a link that might be useful: Mycelium

Fran, also make sure your irrigation is reaching that end of the bed. We have had unusually strong winds from the southeast for the last several months, and I lost a Chestnut Rose because the overhead sprinklers were no longer reaching as far due to the wind.