Brian Duffy will take over day-to-day U.S. operations as CEO of the Greenberg Traurig lawfirm as Richard A. Rosenbaum assumes the title of executive chair as strategic leader, the firm announced Tuesday. Duffy, who previously served as co-president, will split his time between the firm’s New York and Denver offices. Ernest LaMont Greer of Atlanta assumes Duffy’s previous role as co-president with Miami’s Hilarie Bass. Miami partner Larry Hoffman, founding chair, continues in the role Co-chairs Cesar Alvarez and Matt Gorson assume the title senior chair. Bradford D. Kaufman of Palm Beach takes on the new role of global chair of professional development and integration. The changes are effective January 2016.