Aphids & black spot fungus on rose
Roses are host to a wide range of insect and disease pests. The following Oregon State University Extension publication "Controlling Disease and Aphids on Your Roses" was published in 2000 and gives basic information about rose care. A pdf version also is available (click on "print version" link to download the pdf file).
For most gardeners aphids and black spot leaf fungus will be your main concerns. Another fungus, powdery mildew, can become a problem for some roses, in some years.
The very best treatment for aphids is overhead watering combined with insecticidal soap. Use the "wash-soap-wash" procedure described for spider mites. It works great and is non-toxic to you and to beneficial insects and mites.