Sounds all the world like an Aphid infection. They often leave or cause a blackish mold on the infested plant. Alternatively, the bent heads are often associated with Thrips... at least here in the U.S.
The best defense for both is to prune the infected canes severely and then spray the bush with a good insecticidal soap.. I use Neem Oil, since it's all natural alternative to chemicals and works very well. You do have to be persistent and spray the mixture about everyother day for a week or so to get the larvae of both insects. Be sure to spray on the undersides of the leaves as well. It won't hurt to fertilize them lightly. The best way, in my opinion, is to use the smallish rose fertilizer spikes that one pushes into the ground around the base of the plant... seems feed mor consistently.
Best of luck!