How to add roles in dashbuilder?

Issue

• In our application, different use cases deployed in the BPM server and each of them having separate report. While creating the page , we can assign the Privileges to the same at role level not at user level, Due to this, let’s say each use case we have created with separate user with user role, If the specific user logged in he/she can view other use case reports as well as role is same . How to create custom roles/use case centric roles.