One of my bikes has "rollerbrakes" (commuter bike). When I brake very gently, they work silent. If I squeeze the brakes a liiitle more, I hear a terrible metal to metal screaching sound. It makes pedestrians jump out of the way, which is an undesired side effect (well, most of the time). Should I adjust them? grease them? replace them? ...
Roller Brakes (a form of drum brake) do need a regular service, which does require grease (yes it does seem weird to grease brakes) as there are some moving parts that can rub. You should be able to buy some Roller Brake grease/oil and apply to the appropriate location. I am not 100% familiar with Roller Brakes, so you may need to check the location in your manual, or perhaps someone else can help out with the description of rubber cover if needed.
That metal-on-metal sound means you need to inject some grease into your roller brakes. I have roller brakes on my cargo bike and I need to put grease in every second month, especially during summer. There is a grease port (hole) on the outside casing of the brake, you just squirt the grease in there. See the exploded view of a Shimano roller brake - the grease port is marked (6).
It's easier to use the official Shimano brake grease because it comes in a squirt tube, but if you can't get any just use auto grease and inject it with a syringe. Any grease is better than none.
Also be aware on some bikes the grease port is obstructed by the frame, you may need to remove the wheel to get at it.