That is black spot, Roses need to be sprayed with fungicides prophylactically when the weather is wet and humid.
Remove the affected leaves from the plant and from the ground. Wash your hands. There are some products that are available specifically for roses. I prefer sulfur myself as it is easier to find than dithane and I have a harder time cleaning my sprayer when it has oil in it. Daconyl works better in combination with a fungicide than alone. Prune your roses into a vase shape and open it up more so air can circulate. Some varieties are more prone than others. It is humid most of the time where I live so I select roses that have glossy leaves. They just do better than matte leaves.
http://www.missouribotanicalgarden.org/ ... -spot.aspx
http://www.rose.org/rose-care-articles/ ... blackspot/
Happy gardening in Hawaii. Gardens are where people grow.