Allan Kozinn's New York Times obituary includes this:
As a cellist, Mr. Rostropovich played a vast repertory that included works written for him by some of the greatest composers of the 20th century. Among them were Shostakovich Cello Concertos, Prokofiev’s Cello Concerto, Cello Sonata and Symphony-Concerto, Britten’s Sonata, Cello Symphony and three Suites. He also played the premieres of solo works by Walton, Auric, Kabalevsky and Misaskovsky, and concertos by Lutoslawski, Panufnik, Messiaen, Schnittke, Henri Dutilleux, Arvo Pärt, Krzysztof Penderecki, Lukas Foss and Giya Kancheli.
As if that list wasn't amazing enough, for its variety as well as its length, there's this:
Mr. Rostropovich always said that one of the principal lures of the podium was that the orchestral repertory seemed so vast when compared with the cello repertory. But he did not confine himself to the established classics. He commissioned regularly, and led the premieres of more than 50 works. Two of the pieces written for him during his National Symphony years — Stephen Albert’s “Riverrun” Symphony and Morton Gould’s “Stringmusic” — won Pulitzer Prizes. Leonard Bernstein, Jacob Druckman, Richard Wernick, Gunther Schuller and Ezra Laderman were among the other composers who wrote for him, or whose works had their world premieres under his baton.
He will be missed, but his artistic legacy remains as comfort, inspiration, and living memorial.