This new development seems to show that despite his denials President Trump was not buying Rosenstein's story.
Deputy Attorney General Rod Rosenstein has verbally resigned to Chief of Staff John Kelly in anticipation of being fired by President Trump, according to a source with direct knowledge. Per a second source with direct knowledge: “He’s expecting to be fired,” so he plans to step down.
Background: Rosenstein talked last year invoking the 25th Amendment and wearing a wire during Trump meetings, the N.Y. Times' Adam Goldman and Michael S. Schmidt reported last week. He denied both allegations.