Black spot is a fungus among us and poor air circulation and damp foliage encourage this disease. Some roses are more resistant than others. Try removing all the infected leaves, cleaning all fallen leaves as well. In winter use a dormant oil spray on your roses and in spring use a fungicide spray following instructions. Do not wet the leaves when you water and do not crowd the plant. If all this fails then consider removing the rose and planting more disease resistant varieties such as the shrub or landscape roses. Keep growing, Marianne Binetti