oh god. the dreaded cyan banding. ugh. it brings back chills. its a profiling issue. i printed like 10,000 sq/ft of light to dark fading cyan last month.
cyan is a complete mess to print. we got some help with our profile and made it work. took a lot of time, and we still had banding issues. cyan is so sensative that even the pressure the take up reel put on the media coming out of the printer would cause banding if it wasnt perfectly straight etc.
i cant help you with the roland as we run mutohs, but i can tell you that you should be able to "profile it out". its not a heater issue. trust me.
from what i understand, the registration of the dots being shot on the media is very critical with cyan. i was even told by an offset printer in my complex, that cyan is the worst for him too. what you are seeing is the magenta and the cyan dots not meshing perfectly. if you look close at the streak/s you will see exactly what im talking about.
we lowered our print resolution which helped and used different wave patterns, etc etc until we got it as good as we could.