The rain is the reason for the black spots. Picking off the leaves help but when the weather is humid and wet, you would need to use a preventive fungicide. I prefer to use sulfur every 7-10 days while the humid weather persists. You need to spray early in the morning since sulfur in the heat of the day can cause the leaves to burn. Applestar says a spray of milk also works, I use 2% milk, the fat helps to coat the leaves and wick off water. You will have to spray more often since it will be washed off faster by rain or water.
If the leaves have large holes in a lacy pattern they may be eaten by rose beetles. Planting the rose near a light helps.
Bright light deters them. The light only needs to be on from dusk till 10 p.m. If you use a dim light like a solar night light it will attract them instead.
You can under plant the roses with garlic or garlic chives, dwarf French marigolds, and four o'clocks nearby. The scented plants deter bugs. Four o'clocks are trap plants for beetles. If they attack the four o'clocks, they die. Four o'clocks are purely ornamental and are toxic so they need to be kept away from children and pets. They bloom in the afternoon and night.
Other flowering plants like alyssum, dill, fennel, and sunflowers will attract beneficial insects to the garden to help keep pests under control. If you go this route, you cannot use more toxic pesticides since the beneficial insects will also be killed.
If you do not have pets or children, and the other controls are not working, I would use Bayer All in One systemic rose care. It takes care of black spot and the beetles and mites that show up this time of the year. It lasts about 8 weeks. It can only be used on ornamentals so read the label carefully. I comes in liquid and granular forms. It is very expensive. Since it contains Imodicloprid, disbud the roses while it is active so as to preserve the bees.
Happy gardening in Hawaii. Gardens are where people grow.