I know the MT-32 and my MT-200 both have linear regulators in them. I use the newer PSB-120 Roland bricks with my modules. The exception is my SD-20. I came with its original jpn adapter but as I actually have about 123v average coming into my home I didn't want to use it. So for my SD-20 I use an old sega Genesis model 1 PSU.
I've not held an SC-55 in my hand so I don't right off what amperage it requires. But my MT-200 needs 1a on its specs.
I actually use a single power supply brick for my Sega Genesis, SegaCD, and 32x. It is a converted gamecube power supply. That supply puts out 13v at 3a. Plenty to drive all three devices at once. So I would imagine something like that could easily be done for a Midi tower of modules. Just have to see if they all use the same input voltage and add up their required amperage. Then get a PSU that puts out the needed volts and combined amps and splice away with adapter wires to each module.
I've heard that a PS2 slim power brick is also a good candidate for something like.
Midi Modules: MT-32 (OLD), MT-200, MT-300, MT-90S, MT-90U, SD-20