The unveiling of the agency follows Publicis Groupe winning the integrated digital account for JPMorgan Chase, although the shop will "selectively pursue additional clients".
Sean Reardon, the former president of strategy at Zenith in New York, will run the agency as president.
Reardon will report to Rishad Tobaccowala, the chief strategy and innovation officer at VivaKi, and Tim Jones, the chairman and chief executive of ZenithOptimedia North America and the chairman of Performics Worldwide.
The agency will have offices in Atlanta, Chicago, Boston, London and Hong Kong.
Tobaccowala said: "Roar has been created to meet specific client needs, while delivering the alchemy that comes with combining insight, emotion and technology to transform the business of our clients."
Madeleine Freind, a former partner at the translation company Rosetta, will become the agency’s executive vice-president and lead across digital activities and head of client service.
Roar’s media business will be led by Eric Pisick, who was the senior vice-president and managing director at ZenithOptimedia in the US, as the executive vice-president, media.