Currently it's only possible to have one role per admin user, which is quite difficult to handle if you have multiple users which have overlapping roles.
E.g. we have usually Editors and Sales people. So we need two roles. Besides that we also have people who're allowed to do both, so we already have to maintain three roles which have a very big overlap in the ressources. We always have to update all the roles if something in the ressources changes. This problem gets even bigger if you have three or four normal roles which have to be mixed up.
Also the ressources which everyone should have, like the section to change the own password has to be added to every role individually instead of just having a "my account" role which you have to maintain only once and add it to every user.