It is really important to fertilize your roses. That is how your roses get their much needed nutrients. Roses are much like people in the things that they need in order to remain healthy. Just like people they need water and food (fertilizer).
Most types of roses have to be fertilized frequently to keep them growing at a fast pace. You should fertilize with a fertilizer that is slow to release like fish emulsion or Osmocote at planting time. Be certain to follow the instructions properly from the label.
Avoid over fertilizing during the winter because by trying to promote new growth in the winter will make your roses more available to freeze damage.
Important Tip: You should never fertilize plants that are heat or water stressed. Water stressed plants that grow under a lot of heat will cause leaf and bud burn.
You want a steady temperature of approximately 70-80 degrees because your plants will get the most nutrients that are available to the plants. During the growing season, you can give the plants a water soluble fertilizer every two weeks.