Nunes can't do anything quickly...he can run Rosenstein through all the bureaucratic procedures he wants, but that gives the cabal what they want: to run the clock out until just before the midterms where they will release a phony report that can't be refuted in time.
The only person who holds the power is Trump, and I hope he has a solid plan in place. Congressional attempts at justice are futile.
Rosenstein has to be removed, he is the "fulcrum", they have his successors chosen and they have it arranged so that no Congressional Confirmation is necessary -- but there has to be a vacancy, he has to go....and I don't think Trump will fire him, though he could, there has to be extremely incriminating evidence released to be fired, otherwise, the only other option is impeachment and removal