Well he's not central in Hillary's emails but he is said to be central in the plot to cover up Hillary's email crimes and divert the investigation to help achieve the cover up.
And THAT is what this IG report is about. So I think he may be central to this report. At least, I hope he is... and that he is fired or recused tomorrow.
If he is the one to present the report to Trump, do you really think that Rosenstein will be implicated in any way? This is the deep state investigating itself. I expect a whitewash.