Project Server 2010 - PWA Creation Failed

Scenario:
When trying to provision a new PWA. It fails on Provisioning Databases stage. Event
viewer records the below errors,

Microsoft.Office.Project.Server.Administration.ProvisionException: Failed to provision databases. ---> Microsoft.Office.Project.Server.Administration.ProvisionException: IF NOT EXISTS (SELECT name FROM sysusers WHERE name = N'ProjectServerRole' and issqlrole = 1)
BEGIN
EXEC sp_addrole N'ProjectServerRole', N'dbo'
END
---> System.Data.SqlClient.SqlException: User does not have permission to perform this action.


Root cause: The farm account used to execute the PWA creation command does not have sysadmin privileges on the database instance.

Solution: In our environment no account is allowed sysadmin privileges, although it is clearly mentioned as a requirement for Project Server 2010, http://technet.microsoft.com/en-us/library/cc197607.aspx
We have decided to grant the farm account db_owner permissions manually on each of the 4 pwa databases and then Retry the provision process.