Roberto Díaz is currently the president/director of the Curtis Institute of Music, of which he is an alumnus. From 1996 to 2006 he held the position of principal violist of the Philadelphia Orchestra, and previously was principal viola of the National Symphony under Mstislav Rostropovich, a member of the Boston Symphony under Seiji Ozawa, and a member of the Minnesota Orchestra under Neville Marriner. He is the violist in the Díaz Trio, which also includes his brother Andrés Díaz, a cellist, and violinist Andrés Cárdenes, concertmaster of the Pittsburgh Symphony Orchestra. Roberto Diaz's recording of transcriptions by William Primrose with pianist Robert Koenig was nominated for a 2006 Grammy Award. Díaz was born in Chile.