Ouch... Sorry.
That has got to be an increasingly difficult problem, these days, eh? About the only workaround I can think of there is that most functions and style selections, etc., can be called up with MIDI, so some kind of tactile MIDI control box might be able to be programmed to call touch screen functions...
Roland tend to bias their OS towards the 'one registration per song' system (although you CAN do 'free-panel'), so you CAN call up UPGs (reg's) using panel buttons and two spots on the touch-screen (bottom left and right) - for paging. You would bottom left a bunch of times to get to page one, then count bottom right beeps to get to one of 10 or 12 pages, then panel select the choice there.
But I can only imagine how difficult it can be to operate one of these without sight. You might be better served going back to an older arranger (G1000, perhaps) that still sounds good, but relies on buttons a lot more...
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An arranger is just a tool. What matters is what you build with it..!