I'm not exactly sure how to intend to map roles to their permissions, but if they are predefined, you'll want something like:

definition user {}

definition region {
  relation sales_manager: user
  relation sales_clerk: user
  relation accountant: user
  ...
  permission edit_order = sales_manager + accountant
}

definition order {
  relation location: region
  permission edit = location->edit_order
}