I would consider getting used to roughness, since you will be needing it a lot, and it is weird to invert a common convention.
But to answer the question: I think for the buffer visualization you need to dive in c++. You could also make a custom post process material and use the scene texture node → roughness, invert it, and plug it in as your final output. But like I said before, getting used to roughness is the better option.