Hi,
in my project requestor was a person who was requesting a role creation (request itself was created outside from BRM standard solution). Newly created role inside BRM is sent for approval of Role Owner during 'Role approval' step inside BRM role creation methodology. Of course you will have to setup such a stage inside role creation methodology.
Role Owner is assigned to role under first step (Role definition in tab owner/approvers). There are two possible kinds of role owners (assignment and content).
Based on this assignment system later in the role methodology creation phase Role approval is sending an request for approval to Role content owner.
Hope this helps,
Filip