Cool!
But where did you get the model? It isn't downloadable from SketchFab, and Babylon.js gives a clue to
only the .glTF itself but no associated .BIN and textures... all the assets!
I think the JPEG that goes under the name
roughness.jpg is in fact a multi-layer map with more layers to it than just "roughness". It should have one more layer called "metalness". The green-blue coloration proves it.
Photoshop it into two grayscale images of blue and green channels and call them "roughness" and "metalness". Use SketchFab's Model Inspector to determine which is which.