Hey SoraJr,
You mentioned you attempted to plug in a single constant to the Roughness input. Could I see a screenshot of the material applied with a single constant vector with a roughness of 1.0 as its input to one of the walls or ceilings in your scene? In order to assist you with issues like these, we will always ask for some screenshots of the issue occurring in the project as this will help us determine the appropriate course of action.
Thanks,