Any termination or resignation of Rosenstein has the potential to affect the special counsel's investigation into possible co-ordination between Russian Federation and the Trump campaign since Rosenstein appointed former FBI director Robert Mueller to the job of special counsel and closely oversees his work.
The group discussed violent crime in Chicago, support for local law enforcement, border security, the police chiefs' conference they were flying to and "general DOJ business", spokesman Hogan Gidley said without elaboration. "We'll be talking on the plane", Trump said.
Rosenstein left the White House with his job that day.
"The press wants to know, 'What did you talk about?'" Trump said at the start of his speech after he thanked Rosenstein for being there and noted the intense media interest.
Fresh off his victory of Judge Brett Kavanaugh's confirmation to the Supreme Court, President Trump doubled-down on his commitment to being the "law and order" president by suggesting Chicago could curtail gun violence by using "stop and frisk" - the famous NY law enabling officers to temporarily detain, question, and frisk civilians upon "reasonable suspicion".
Rosenstein and Trump had been expected to meet at the White House days later, but that meeting was put off so that the president could focus on a confirmation hearing of Supreme Court nominee Brett Kavanaugh.
Trump had previously indicated he would prefer to keep Rosenstein in his post, but offered no definitive indication of Rosenstein's fate until his comments on Monday morning. "I know the law enforcement people in Chicago and I know how good they are, they could solve the problem if they were simply allowed to do their job and do their job properly", he said. Upon landing, Rosenstein was seen smiling and appeared at ease as he walked down the front stairs of Air Force One alongside Trump's chief of staff, John Kelly.
The speculation over Rosenstein's future concerned Democrats, who feared that a dismissal could lead to Trump curtailing Mueller's probe.
Trump added that has a "good relationship" with Rosenstein and that there's been "no collusion".
But even as Trump has chose to leave Rosenstein in place - for now - the matter of what Rosenstein said and proposed doing likely will remain a political issues heading into the homestretch of the midterms - and beyond.