OBS can be associated with Team through the ‘Staff OBS Unit' attribute.
The reason for using this is to pre-set the OBS filter in Resource Finder - you can always override this.
Out-of-the-box (OOTB) the default is set in the ‘Default Staff OBS Unit' attribute on the Settings subpage of the Project Properties. This attribute sees OBSs that are associated with Resources. The idea here is you can set the most common OBS node that you're going to use on the project.
When you add a Role to the Team, the default you set on the Settings subpage will populate the Staff OBS Unit but you can override this if required. If you add a Resource it defaults to the unit specified on the Resource Properties.
If this is used properly, you can get away with fewer Roles and just use the Staff OBS to direct the search in the right area of the business, instead of having multiple role variants based on organisation.
Hope this helps.
Regards,
Steve