Not using the printer for months has clogged your heads. Keep in mind that solvent printers make great outdoor durable prints but the down fall is that the ink dries very quickly when exposed to air. The maintenance parts are designed to prevent this from happening but they are not perfect. Usually you can get away with a week, maybe two before you start to lose nozzles that will be hard to recover.
You are going to have to do a head soak and possibly replace some of the maintenance parts. A head soak can be done two ways. I prefer to crimp the waste tubes off so nothing can flow through, fill the cap tops with cleaning solution and then dock the heads on the cap tops. I usually wait no more than 45 minutes and then un-crimp the tubes and run a hard cleaning cycle. The older Rolands are harder to do this on because the cap tops are motorized. You might have the special tool that makes it so you can rise and lower the caps manually. That is the best way to go.
The other way to do a head soak is to soak a lint free cloth in cleaning solution, lay it over the cap tops and dock the heads. I do not like this way as a tech but many people do it this way. It doesn't allow the ink to wick up into the head as well and I just don't like physically touching the nozzles with anything.