Sorry that either Role or Contact Group will track individual openings. Role will at least show 1 open, contact group will not even show that 1 open. You will have to extract all the individual name and email and add them directly as subscribers.
But I do want you to know, this feature has been enhanced a lot in V10 which is bit different than v8. In v10, you can only select contacts or contact groups (no more users, roles as those are not really OM type of features). And I've tested when add contact group to the "recipients" list (not called subscriber anymore), the report does track individual email opening and click through.