Roses should be fed and dead-headed after the blooming season. Feeding them alfalfa meal, Maxsea, or EB Stone Rose and Flower Food are all good choices. Remember, roses should be well-watered before fertilizing.
Foggy nights after warm days can encourage fungus (disease). Keep the area beneath roses clear of fallen petals and leaves. Cut off any leaves with rust, mildew or black spot and drop directly into a paper bag, if possible, and put them in the garbage. Ordinary compost piles will not get hot enough to kill the spores. Thinning the interior of the plant is also a good idea to improve air circulation. Remember to sterilize pruners with alcohol after each cut to prevent spread of the disease.