Well personally I have always made diffuse textures with no shadow or specular information. Just good practice. With PBR it’s just more important.
I’m aware of the values between black and white for roughness, of course. I felt my post was clear (maybe not) - I agree with roughness being one of the more difficult - I advise you paint roughness in an application in which you can see the results in realtime (Substance Painter or Substance Designer) unless using a flat roughness, which can be fine for many things.
if using a roughness map, remember to turn off SRGB
PBR is great tech, and I was pretty lost at first too, but it definitely feels more natural