If they force/fire Rosenstein, it doesn’t matter what Mueller discovers, the investigation findings can be quashed. Even if Mueller finds Trump guilty of impeachable offenses, according to the regulations governing the special counsel’s office, the referral must be approved by the Justice Department. According to Talking Points Memo
If Rosenstein is fired or steps down, Trump would appoint his successor. And if Rosenstein recuses himself, the ranking official in the department of justice (DOJ) would be Rachel Brand, a Republican legal operative who worked in the George W. Bush White House*. Brand then would decide whether or not to send Mueller probe’s findings against the president, if any, to the House.
This, I think, is their end game. They will allow Mueller to finish his investigation, then bury the report so deep, it will never see the light of day. This Nunes memo is the opening salvo in the plot to remove Rosenstein and to protect the traitorous Trump administration.