He has performed under the baton of prestigious conductors like Wolfgang Sawallish, Riccardo Chailly, David Zinman, Richard Hickox, Rafael Frühbeck de Burgos, Christopher Hogwood, Michael Stern, Christof Eschenbach, Bernard Labadie or Hugh Wolf, amongst others. He has worked as well with contemporary composers such as  Krzysztof Penderecki, Edison Denisov or Roberto Sierra.

Mr Díaz has played in recitals at concert halls in New York, Boston, Los Ángeles, Washington D.C., Philadelphia, Chicago, Helsinki, Munich and Moscow. As chamber musician, Roberto Díaz has played together with notorious artists such as Emanuel Ax, Yefim Bronfman, Yo-Yo Ma,  or Isaac Stern, and was invited by this last one to play at the Carnegie Hall centenary show. He has been guest musician at festivals like the Mostly Mozart at the Lincoln Center, Marboro, Spoleto, Verbier, Kuhmo, West Cork or Angel Fire.

He has taught various courses at the Sheperd School of Music at Rice University, at the Peabody Conservatory at Johns Hopkins University, and has recorded for labels such as Naxos, Dorian y New World Records.

Roberto Díaz plays a 1973 Camilli viola, and a 1595 Camilli viola that was owned by William Primorose.