I apologize for this delayed reply to your gardening question and hope it is still helpful to you.
You a rose bush may have suffered a temporary drought were even more likely a bout of foliage disease problems. Like spot is a common rose disease that causes the leaves to develop spots on them turn yellow and fall off the plant. Some varieties are naturally resistant but most varieties require spraying to prevent the disease. As your plant develops new leaves will need to spray with a fungicide periodically to protect them against the disease. Your local Home Depot garden center carries a number of these products. Some examples include Funginex and Bayer Disease Control for Roses, Flowers & Shrubs Concentrate.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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