Hey Julio,
Revit is great for doing quick models but it's terrible for directly importing into Unreal Engine 4, because like you said the materials are all the same when changed in UE4. As far as I know there is no UV Mapping in Revit and that's causing the materials to be all the same in UE4.
You either have to export it out of Revit into 3DS Max or if you don't have that you can try Sketchup which has a free version.
There are a heap of tutorials on the internet about UV Mapping in 3DS Max and Sketchup