Roles of an Organization

 Hi 

When I create an Organization in oim, I can see some groups listed under Available Roles tab of the organization screen. Among these, few roles were created by us, and few roles seems to be system defined. 

I would like to understand, 

1. How these roles are being populated?

2. How I can assign, roles of my own choice to the organization during creation of it?

Quick inputs on this are highly appreciated. 

We are using 11gr2. 

Thanks & Regards

YK