My understanding is that retaining Rosenstein makes him available to the DOJ Inspector General. I can imagine many questions for Rosenstein.
My take. I think Barr has Rosenstein by the shorthairs and Rosenstein knows it. He is Barr’s Bitch. Barr is going to allow him to spill his guts and try to retain some sense of dignity. If he doesn’t I’m sure Barr will destroy him.