Rosen, who takes up his role in November, will be responsible for leading and developing Telefónica's advertising businesses globally and will focus on Europe and Latin America.
He said: "Telefonica is one of the world's leading mobile operators, not just in size and influence but also in digital disruption and innovation. With mobile occupying a more central place in people's lives than ever before, and Telefonica transforming itself into a digital telco, there could not be a more exciting time to join."
Rosen has 20 years of experience working with brands to improve their mobile and integrated communications and has been with Joule since 2012.
Prior to this, Rosen was the founder and head of AKQA's global mobile practice for eight years, working with Nike, Gap and Volkswagen. Previously, he was managing director of Associated Newspapers' interactive subsidiary, Greenland, and he began his career as a marketer within Orange UK.
In his new role, Rosen will report to Stephen Shurrock, Telefonica's chief executive of innovation and digital disruption.
Shurrock said: "I am delighted that Daniel is joining Telefónica. He is a major player in mobile advertising and his appointment underlines our commitment to drive the growth of mobile advertising globally.
"Daniel's experience and deep understanding of mobile will help us further accelerate revenue growth and product innovation, and build even closer relationships with the brand, publisher and agency community," Shurrock added.