hiding sheets by role

Why don't you try creating separate audiences for each group? You can do this while creating or updating the app in the Power BI service. This doesn't work if the end users are in the workspace, but if they are just trying to view the reports using an app would be the best solution anyways. 

To be able to hide the different pages of a report you would need to post the pages to separate dashboards, but once you already have your report written this is a simpler solution than recreating navigation inside of your report. 
Or, you could also create separate reports for each audience using the same semantic model. That way when you have a refresh scheduled it only needs to go through once. If everything is set up correctly you should be able to just copy and paste your visuals from one report to the next.