In 1980, he became president of the New York agency and in 1985, he was named chief executive officer of BBDO Worldwide.
[5] In April 1986, He spearheaded what is dubbed as advertising's "Big Bang,"[6] a merger that created the Omnicom Group, the world's largest three-network conglomerate consisting of BBDO (Ranked No.
[10] Under his leadership, BBDO was selected "Agency of the Year" in 1982, 1984, 1993, 2000, 2001 and 2005 by various industry publications such as Ad Age and Adweek.
[5][11][12][13][14] In 1991, he served as president of the jury of the Cannes Lions International Festival of Creativity.
[15] In 2006, Rosenshine announced his retirement from BBDO and retains the title of chairman emeritus.