Answer: Unfortunately, based on your description I am not certain what is happening to your roses. Roses need full direct sun all day, so that is good. They also need good air circulation. Watering should be done as needed to keep the soil evenly moist; it is best to water them deeply less often than to water lightly every day, and to avoid wetting the foliage when you water. Using an organic mulch several inches thick in a flat layer over the root area will help reduce watering needs and also help feed the soil slowly as it breaks down over time.
Browning foliage can be a sign of over or underwatering, it can be a sign of overfertilizing, or it can be a sign of a disease (in your area, black spot is prevalent) or an insect problem. It can also be caused by accidental chemical exposure or herbicide contact, or by applying foliage feed or other sprays during hot sunny weather.
The following web page has a diagnostic chart that might be helpful for you.
I hope this helps you trouble shoot. I'm sorry I can't be more specific for you long distance.
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