With your permissions structure, you would still need to do a check for both.
You need to do the check for both because of the bizRule associated with the 'owner' role. Even if someone has admin permissions they will not be able to pass the bizRule and therefore will not validate for that permission.
In this instance, making the 'owner' role and child of the 'admin' role does not add any benefit because of the bizRule.
What I do in situations like this is actually make the operations children of the 'admin' role, rather than making the 'owner' role a child of the 'admin' role.
So something like this:
// owner role
$bizRule='return (!Yii::app()->user->isGuest && Yii::app()->user->isOwner);';
$role=$auth->createRole('owner', 'business owner', $bizRule);
// admin role
In this way, admin still will validate for those operations but does not have to satisfy the bizRule associated with the 'owner' role.
Then, on your controller, you could simply check for the specific operation you wanted (such as 'updateBusiness') and it will validate for both admins and owners.
One thing you should note, though, is that to do the cascading of permissions required multiple database queries using the RBAC. It can be, depending on your permission structure, fairly heavy to check for individual operations rather than just roles. Because of this, you should try to keep your permissions structure fairly flat. This will decrease the load associated with checking for permissions.