Hi Bruno,
Sorry but I'm not wild about this idea. A users role membership is security information that I don't think should be tracked and also users can be in multiple roles.
A developer could add additional tracking by adding javascript to push tracking into the array added at the top of the page by the async analytics controls. But I would not recommend tracking roles and do not want to bake that in. It is sufficient to be able to tell authenticated members/customers from admins and unauthenticated users as it works currently.
Best,
Joe