Rod Rosenstein did not lie in his memo explaining the firing of Jim Comey. He only wrote what he needed to write.
Trump had just conducted a victory lap with Russia at the Oval Office and provided payment in full to Putin for his election by releasing classified documents to Russia.
Is there really a question where Trump's loyalties lie? No one ever asks Trump who he is loyal to. Why?
Rod Rosenstein would not write that the Comey investigation into Russian influence in the 2016 election was the reason for Comey's firing, because, you never elevate your enemy to a level of influence. Russia has an influence on Trump. In including Russia in an FBI memo as the reason for firing the FBI Director it would prove to the world that the USA is now Russia's puppet. Rod Rosenstein is not Russia's puppet. The integrity of the FBI and it's investigation remained and continues intact, regardless of Trump's loyalty to Putin and Russia.
If Rod Rosenstein had written that James Comey, the Director of the FBI, was fired because of an investigation, it could have stopped everything and put others within the organization at unease regarding the continuing investigation and their role in it.
Rod Rosenstein, by leaving out the word Russia, in his memo explaining the firing of the Director of the FBI, James Comey, protected the agency and the country. Rod Rosenstein is a hero. He didn't have to fire a shot and he didn't lead a military into battle, but, the early days of the Trump administration demanded heroics and Rosenstein was prepared to be that hero. The country owes a great debt of gratitude to Rod Rosenstein. He was passed over to promote to US Attorney General because he loved his country. Trump was trying to coupe the USA Constitution and Rod Rosenstein would not have any of it.
It could be said if Rod Rosenstein had included Russia in that memo it would come back to haunt him as it was proof Trump obstructed justice. If Trump were accused of obstructing justice, Rosenstein could be dismissed immediately as Trump refused that assessment in his memo. Either way, Rosenstein should be US Attorney General right now and the country is hurt because he is not.
And that is the truth.
