Sorry to disagree with Eric, but if you have recently planted this rose and now it's getting a lot of rain and no sun, your problem isn't feeding, it's that your rose is drowning. If you planted it at ground level, it may have sunk a bit and the planting hole doesn't drain well. If you take the rose up and place it in a large terra cotta pot where it can get some sun and regular watering with good drainage you should see some improvement. If it has already rotted at the roots, and you'll be able to tell when you take it up, you may have to replace the plant. The roots need air as well as water and that's why you should always amend your soil with plenty of compost and leaf mold when planting roses. Also, usually the planting hole should be about 3 times as large as the diameter of the root spread. When planting, you want to form a hill of soil in the middle of the hole and spread the roots around the sides of the hill, then fill the hole with the amended soil mixture. This provides drainage and air for the roots, and micronutrients necessary for large, colorful blooms and healthy green foliage.
Other organic amendments you could use are bone meal, blood meal, lava sand, Texas greensand, cottonseed meal and well-composted animal manure.