SQL Server account permissions for New ReportServer database from wizard I'm trying to create a ReportServer database on a different server (Server_AT) other that my Reporting Service server (Server_RT). 
ON Server_AT, I created the RSExecRole as per the script here. Then created a login 'Reporter' with user 'Reporter' and assigned the RSExecRole.
Now when I use the configuration wizard -> create a new ReportServer database-> enter the SQL Server credential for Reporter as prompted-> and finish. 

Now the process fails - constantly with on error after another that one of permissions in the RSExecRole cannot be found.
The ReportServer database does gets created on Server_AT but the user is dbo- but I am not able to connect to this database either (when I try next time).

What am I missing here?
@Kin- Thanks for your answer. I was able to refer to this from your answer and get it resolved.
https://social.technet.microsoft.com/Forums/en-US/7541b1ce-aff8-4385-9544-8f9422d01ba7/cannot-alter-the-role-rsexecrole-because-it-does-not-exist-or-you-do-not-have-permission

The fix is weird- this basically covers all the permissions that are collectively included in the RSExecRole but somehow works when executed invidually. Weird!!