Consider the lunacy of this: By providing Trump with a memo justifying Comey’s firing, Rosenstein participated in the scheme that the FBI considered a possible crime or the culmination of a Russian plot.
Then, Rosenstein turned around and appointed a special counsel, whom he oversaw, to investigate the possible crime to which he was a party.
It’s also absurd that the FBI officials considered the firing of Comey to be potential obstruction of the investigation that they were continuing and, indeed, making more serious by making the president an explicit target.
The comments that Trump made about Russia that McCabe and Co. found so disturbing were hardly damning. In his cover letter over Rosenstein’s memo, Trump mentioned that Comey had told him three times that he wasn’t under investigation. This was true, and Trump was frustrated that Comey wouldn’t make it public. That doesn’t make Trump a Russian agent.