Five facts are indisputable. First, Rosenstein is currently supervising Robert Mueller, who he appointed to be special counsel to investigate the Russia matter and all ancillary issues. Second, these ancillary issues include any possible obstruction of justice growing out of the Russia investigation. Third, President Trump’s firing of former FBI Director James Comey may be an important building block in any possible obstruction case against the president. Fourth, Rosenstein played a central role in that firing, having written the memorandum justifying the president’s action. Fifth, Rosenstein would be an important — perhaps the most important — witness in any investigation of the reasons behind the firing.