Kaufmann will become director of client development for North America, based in Chicago, the same city where she joined the agency 20 years ago. The Cleveland, Ohio native had become London CEO in March 2013.
She remains on the Omnicom firm's global leadership council, to which she and 19 others were appointed on two-year terms in June 2016, although said it was still to be decided whether she would remain after her term concludes next summer.
Robertson was named deputy CEO of Ketchum London in 2015, having joined as MD of corporate and public affairs in 2011 from Weber Shandwick.
She began her career as a political activist with the Labour Party, and has since taken secondments into the party's campaigns during the 2005 and 2010 general elections, and worked as a TV reporter in her native Scotland.
The pair of moves come after Omnicom CEO John Wren said that there would soon be leadership changes at the top of one of the group's PR agencies. Asked by PRWeek whether there would be further senior personnel moves at Ketchum, Robertson said: "Not that we know of."
Robertson also told PRWeek she had no immediate plans to hire a deputy CEO to work under her. Her executive committee for the UK will consist of her, financial director Gavin Cooper, head of HR Kirsty Sachrajda and COO for London Deirdre Murphy.
Kaufmann is crediting by the firm of driving an integrated setup, which has become a "model" for the rest of the network. She told PRWeek that London was the first Ketchum office to integrate its offering by removing P&Ls, and that "slowly but surely" others in the network were now following suit.
She said: "When I took over as CEO in 2013, that was when we really began to talk about the idea of client-centricity, and once we moved into this building [in January 2016] we started to talk about the 'One London' concept, and removed our P&Ls."
In her new role, she told PRWeek, she will "work to help client directors and client teams to diversify existing client relationships".
Kaufmann will report to Michael O'Brien, who was promoted to chief client officer last year, having previously been North America's director of client development. O'Brien said: "Denise is a charismatic team builder, a creative problem solver, and an extraordinary counselor.
"She is known for delivering top-notch service to clients, having a razor-sharp focus on attracting and retaining the industry's very best talent, and for creating an environment that encourages our employees to reach their full potential."
Robertson will report into will report into Mark Hume, the COO and CFO for Ketchum's operations outside of the US, who is based in london. He said: "Having worked side by side with Denise over the past two years to strategically grow this critical hub for global client engagements, I could not think of anyone more perfectly suited for this role than Jo-ann."