His exit comes after a bombshell report in the New York Times Friday about memos written by former FBI Deputy Director Andrew McCabe recounting Rosenstein a year ago suggesting the invocation of the 25th Amendment, and he would wear a wire with the President. He is now on his way to the White House.
In the wake of the Times report, Democrats have warned Trump not to remove Rosenstein.
"He's expecting to be fired", a source close to Rosenstein told the publication.
The 25th Amendment provides for the removal of a sitting president if he or she is judged unfit to carry out the duties of the office. With Rosenstein's exit, solicitor general Noel Francisco would oversee the investigation.
Rosenstein's prospective departure throws into question the oversight of special counsel Robert Mueller's investigation. If Rosenstein is fired it limits Trump's options.
Trump has spent months publicly attacking Rosenstein as part of a broader battle against federal law enforcement over the Russian Federation probe, which he frequently slams as a "witch hunt". As for Rosenstein's future, Trump says, "We will make a determination".
The amendment deals with presidential succession and disability and outlines how the Cabinet can decide whether a president can no longer do his job. The Justice Department also has drawn attention to other instances in which Mr. McCabe has made statements that later have been proved false. Trump has repeatedly attacked Sessions for that move.
Deputy U.S. Attorney General Rod Rosenstein speaks during the Bureau of Justice Assistance's rollout for the "Fentanyl: The Real Deal" training video in Washington, U.S., August 30, 2018.