It sounds like aphids. Roses are beautiful and yummy to a few pests and diseases. To keep roses healthy they need to be spaced far enough to get good air circulation. Pruned into a vase shape after each bloom cycle to promote more blooms. Fed regularly and make sure they get their micros.
It is very hard to grow roses organically. The best defense is a healthy rose. I find that the hybrid teas are the hardest to grow without systemics. Floribundas (I don't like them, so I only had a few) Grandifloras amazingly were not as hard as teas but they are big plants and required a lot of space. I have learned to buy roses with glossy leaves. They do better with black spot and mildew.
My hardiest roses are the ramblers, shrub roses, and landscape roses. I don't do anything for them. Pests don't really bother them, they rarely get mildew unless the rain lasts for a week and I don't even plant them under lights. Rose beetles don't bother them either. But I don't have that many problems with rose beetles now since I decided to let nature do the work. I stopped using the systemics last Spring. Some pests, like the papaya scale, were immune to the systemics anyway are still there. I pulled out the weakest roses since they always had black spot and kept only the toughest ones. I planted alyssum and I already had false heather. The beneficial insects have come back and the roses are doing o.k. I may have to spray the hibiscus more this summer for the erineum mites, but the rest should do fine.
To deter rose beetles. Plant under strong light. I plant my roses in the front yard near the street light.
Roses are heavy feeders. I use a slow release fertilizer and supplement with citrus food (it contains micros and I use it on everything. That way I don't need to have too many kinds of specialty fertilizers)
Mulch roses to hold in moisture in summer. Water roses deeply. Newly planted roses need to be watered every day for a couple of weeks but established roses can handle once a week deep watering if you mulch. Shallow watering and watering leaves just invites problems.
Prune after each bloom cycle to the vase shape. Make sure tools are clean. It promotes rebloom and your roses will have better air circulation
Plant roses far enough apart that air can move around them. Do not plant them up against a solid object like a wall.
Roses like all the sun they can get.
If you know it is going to rain or it has been raining for a while. Fungicide roses. You can use a horticultural oil or neem as a preventive. They help the leaves repel water. In the summer when the temperatures are above 80 degrees it is best to use a sulfur product. Do not use oil and sulfur within two weeks of each other or the plant will burn.
Aphids are not that hard to take care of. Oil or insecticidal soap will work, but that is too much work for me. I plant nectar plants and hosts to lure natural predators. Alyssum, dill, fennel (fennel needs to be planted alone somewhere it attracts lady bugs but it does not like to be around other plants), dwarf french marigolds, Garlic or onions planted under the roses deter some pests. I don't use neem when plants are flowering, I use horticultural oils instead especially if bees are foraging. Oil works better on scale.
The biggest problems are with diseases like black spot and mildew. If removing and discarding (don't let the leaves drop to the ground. Sanitation is important) the leaves and preventive sprays don't get it under control there are systemics that will work. Fungal infections are hard to cure once they start. Then I resort to the systemics. Systemic rose care lasts for about 6 weeks. Bayer tree and shrub and Bayer 3 in 1 Insect, Disease, and mite control both contain imidacloprid which is harmful to bees and every other beneficial insect. It works for a year. Use it only if you are desperate. It controls both disease and chewing pests.
Happy gardening in Hawaii. Gardens are where people grow.