Help! Invert roughness map and reduce metalness to zero

Hi all,

I am importing models purchased from evermotion into blender 2.82a. I have to invert all roughness maps and reduce the metalness to 0 on all materials, there are over 100 materials in some of the scenes. Is there a way to automate this using an existing addon, if so can anyone point to the addon or, think of a way to automate this tiresome task?

Many thanks in advance for your time.