For species roses, a spring application of general-purpose fertilizer is usually adequate for the season. Spread the fertilizer in a band starting six inches from the crown of the plant, going out to about 18 inches. Work it in lightly and water. All other roses benefit from a second application about June 15 or at the end of the spring bloom period. No fertilizer should be applied after August 15 so as not to encourage soft, succulent growth that could be easily winter-damaged.
Roses can be fall fertilized after the plants have gone dormant.
Applying fertilizer at this time will not encourage growth but will be available as the plants start to grow in the spring. Also by using a fertilizer high in potassium winter hardiness tends to be increased. Nutrient release is dependent on the soil moisture and temperature. Several forms are commercially available.