Answer: My first thougth is are these leaves bottom or interior leaves? If so, it's natural for these leaves to yellow and drop if the rose doesn't get enough sun or the soil is too wet. They like at least 6 hours a day and are best planted on well-drained soil. Also, if you haven't fertilized since early March, I'd give the roses a dose of fertilizer containing a fair amount of nitrogen. Try foliar applying the fertilizer on the leaves for quicker absorption. Also make sure the fetilizer has minor elements such as iron. Sometimes yellow leaves can be a sign of specific nutrient deficiencies. A soil test might help determine the soils fertility. If you don't see any signs of disease, I'd put my money on a nutrient or sun problem.
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