Sessions might be able to fire Rosenstein, I don’t the rules for that case. But if he has that ability, your suggestion that it should be done with just one side of the story (the memo), I would disagree. There has to a be a process for firing, but also a process for prosecution (for Rosenstein). Those will take time.
Rosenstein LIED to a FISA Judge. Its a clear cut crime, fire his ass.