Rosenstein's confirmation hearing came March 8, just days after Attorney General Jeff Sessions had recused himself from the Russia matter -- meaning that Rosenstein's hearing to be Sessions' deputy was suddenly under the microscope.
This week, after Rosenstein guided Trump to fire Comey amid an intensifying Russia inquiry, CNN looked back at Rosenstein's answers at that Senate Judiciary Committee hearing for clues about how he viewed his role and the investigation writ large.
Here's some of what he said two months ago that appears consequential in hindsight.
"Certainly if the president had a conflict in a particular matter I would not take any advice from the president," Rosenstein told Sen. Mazie Hirono, D-Hawaii, when asked about presidential interference in the Russia investigation. "If the president has committed a crime and I believe the president's culpable, then I wouldn't follow the president's advice."
"It's certainly true," he told Sen. Chris Coons, D-Del., when asked if he would resign should he be inappropriately pressured to shut down an investigation. He said he could go public if that happened. "Hypothetically, it would depend upon the facts and circumstances. In an appropriate case, I would."
"If there's evidence, senator, that the attorney general and the president have information relevant to a criminal investigation in this case, as in previous cases that I've handled I'll make sure they're questioned," he told Sen. Richard Blumenthal, D-Conn., when asked if he would be able to investigate his bosses. "I've done that before. I've been involved before in questioning a president of the United States."
"Anybody could call, senator. They're not going to get an answer," he told Sen. Sheldon Whitehouse, D-R.I., who wanted to know if the White House could call him about a case. "The rule, senator, is that the communication should be between the White House Counsel or deputy counsel and the deputy attorney general."
Wouldn't commit to appointing a special prosecutor
"'I've had no communication with the White House at all about that issue, nor have I had communication with the attorney general about that issue," he told Vermont Sen. Pat Leahy, one of many Democrats who implored him to appoint a special prosecutor for the case. "I'm willing to appoint a special counsel, Senator, whenever I determine that it's appropriate based upon the policies and procedures of the Justice Department."
"The authority that I would give to a special counsel would be whatever authority is appropriate to make sure that he or she had the full range of authority to conduct the appropriate investigation that's required and justified by the facts and the law, just like we do in all other cases within the department," he told Sen. Amy Klobuchar, D-Minn., when asked for the scope of a special prosecutor's authority.
"You view it as an issue of principle that I need to commit to appoint a special counsel in a manner that I don't even know if it's being investigated," he told Blumenthal, who wanted Rosenstein to commit to publicly revealing if he chose not to appoint a special prosecutor. "But my view is that I have a responsibility when I take that oath, if I become deputy attorney general. I cannot take it conditioned upon having committed how I'm going to handle a particular case."
Might inform the American people if the investigation concluded
"I don't want to make any commitment about what I would do at the conclusion of investigation without knowing the details of the investigation. Talking with the director of the FBI, I can assure you, that if it's appropriate to release it to the American public, I would," Rosenstein told Sen. Dick Durbin, D-Ill., in one of the hearing's rare references to Comey.
"I highly value our responsibility to inform the American people to the extent we can, so that's sort of my default position," he told Sen. John Kennedy, R-La., who wanted Rosenstein to at least commit to sharing the investigation's conclusions. "If we have lawful basis and it's appropriate for us to provide public information, I think it reassures the public when they know what we've done and why we've done it, so that would certainly be my preference."
Said he did not know much about Russia investigation, but would stand up for America
"Senator, I don't know the details of what, if any investigation is ongoing," he told Sen. Dianne Feinstein, D-Calif., "but I can certainly assure you, if it's America against Russia or America against any other country I think everyone in this room knows which side I'm on."