basically you dont need a PBR shader anymore. The principled shader will do just fine.
However its not that straight forward.https://www.sidefx.com/forum/topic/46543/
In this topic read what: robsdesign wrote
“1. A Roughness Map is White = 1 Roughness Value (not shiny), Black = 0 Roughness Value (shiny). When using the Principled Shader, the Roughness value (slider) seems to determine the strength of the texture used. ie. If you want to use just the roughness values of the texture, set this to 1. However, As your texture map is mostly black, changing from 0.3 to 1 won't show much difference as both result in values closer to 0 (shiny). To fix this, decide what should be shiny and adjust the map (inverting the texture works as a quick example)
2. The Mantra Surface roughness works pretty much the same. The difference here is that you are using a texture in the Reflect Colour. (often used for metallic materials in a Spec/Gloss workflow) Whilst this works to show some difference in your texture, it'll probably need tweaking to work with other textures and lighting etc. I'd recommend looking into Spec/Gloss and/or Metal/Roughness texturing workflows so you can use PBR with more expected results and avoid endless tweaking.
3. The Principled Shader has the benefit of being useful in a Metal/Roughness workflow and I'd recommend looking up information on this as it simplifies a lot of texturing.