Not to hijack a thread, but I believe I recently read that there are a bunch of deputy(?) AG positikns vacant as well. Like 30%? And the rason is they haven’t been nominated. And the person responsible for nominating them is...Rosenstein.
There is only one Deputy Attorney General. You may be thinking of US Attorneys. Interim fills have been appointed by Sessions. The formal nomination and appointment of all positions subject to Senate confirmation is the president. He has of course delegated this all over the place (to Sessions for DOJ, to generals for military, and so on), and for DOJ/US attorney positions, typically input comes from outside the government, as well as from inside.
If Rosenstein is nominating them, we are better off waiting a while.