Does SSRS report user needs database level permission? I have a separate reporting server and a separate database server.  Now on the Reporting server site settings I could see there are some roles and users.  Suppose a User BOB has ‘POWER USER’ role assigned and the user can create and deploy report. 

Now the confusion lies here as I want to remove some database logins does BOB needs to have database level permission (example execute permission and database reader ) on the database and also on the report server database  or the permission assigned to the role on SSRS will be good enough.

Does SSRS report user needs database level permission or the login that is used on the data source will only need database level permission.
the data source login will need permission, the AD used by the user to run the report will not