There are a couple of things troubling the rose in this photo. First, the yellow areas on the leaf indicate that the rose is possibly suffering from a nutrient deficiency. Probably Iron deficiency due to a high pH of the soil (alkaline – salt). There may be iron in the soil but it not available to the plant because of the pH. Second, the brown edges of the leaves looks like a salt burn or underwatering. Again, that word salt…If they are planted directly in the ground, you might want to give them a good deep watering a couple of times a week until you see improvement. If they are in a pot, you would want to water them thoroughly until the water is running out the drainage holes in the bottom of the pot. You might want to start a regular fertilizer program by getting a fertilizer especially for rose plants (that includes iron) and a pH test kit for the soil. Follow all directions on the fertilizer container. Third, the white fuzz on the leaves might be Powdery Mildew (it’s hard to tell for sure from this photo). You might want to take a bagged sample like this into your local garden center for a hands on diagnosis of the problem and possible solution options.