I think the best approach would be ask Sessions to fire Rosenstein.
Then fire Sessions.
Thinking along those lines. Charge Rosenstein with obstruction of justice for failure to comply with Congressional subpoenas. THEN fire him. Next, charge Mueller with treason in Uranium One scandal. Probably can also charge obstruction of justice. Park both of their behinds in jail while sorting it out. Even if it seems to risky to fire them, having criminal charges of their own to deal with could tie them up, and permit investigation of their own communications.
It would help Trump if the Republican Congress would pass a resolution supporting the firing of each. RINOS would probably prevent that, but...