Trump fired Comey in a letter that was hand-delivered to the FBI on May 9 while the law enforcement official was at a bureau branch in LA.
The letter cited a lack of confidence in his ability to lead the bureau as the reason for dismissal, and it included a revelation that Comey told Trump three times that he was not under investigation.
Two other memos in the packet signed by Attorney General Jeff Sessions and Rosenstein, his deputy, backed up Trump's decision.
In three pages, Rosenstein crucified Comey for running the FBI into the ground.
The bureau's 'reputation and credibility have suffered substantial damage' over the past year, Rosenstein wrote, 'and it has affected the entire Department of Justice.'
Rosenstein said he could not defend Comey's treatment of Hillary Clinton's email case and harangued the FBI director for refusing to admit he made 'serious mistakes.'
'It is one of the few issues that unites people of diverse perspectives,' Rosenstein contended.
Among the mistakes Comey made was his decision to 'usurp' Attorney General Loretta Lynch's authority at a July 2016 press conference where he declared 'no reasonable prosecutor' would bring a case against Clinton.
Lynch had recused herself from the investigation following an encounter with Clinton's husband, former President Bill Clinton, at an Arizona airport.
At most, Rosenstein said Comey should have pronounced the FBI's work finished and handed the case to federal prosecutors.
'The FBI director is never empowered to supplant federal prosecutors and assume command of the Justice Department.'
The White House initially laid the firing at Rosenstein's feet. Three senior Trump aides scrambled to spin Comey's canning as Rosenstein's idea on TV that night, only to back track and say it was the president who first brought the subject up.
Trump had been considering a change at the bureau for months, they later said. He acted after receiving oral recommendations from Sessions, who had recused himself from all probes of the previous election, and Rosenstein that he asked them to put in writing.
His administration maintains that it was Comey's mishandling of Clinton's emails - and his inaccurate testimony to a congressional committee - that landed him on the chopping block, not his investigations into the president's campaign and his associates.
