Diederik Rooker began his musical career at the Noord-Hollands Jongenskoor under the direction of Hendrik Timmerman where he as a boy soprano soloist and made numerous tours. Then he studied singing with Maria Rondèl in Alkmaar and currently he attends private lessons with Paula de Wit. Previously, he participated in the World Youth Choir and World Voices, with which he appeared all over the world and sang under conductors such as Eric Ericson, Frieder Bernius and Tõnu Kaljuste.
Currently Diederik Rooker sings with Cappella Amsterdam, the Nederlandse Bachvereniging, the newly established Nederlands Vocaal Ensemble and the Arnold Schoenberg Chor, Vocalconsort Berlin and La Capella Reial de Catalunya. He has worked on various radio, TV and CD recordings. In small vocal ensembles he sang under conductors such as Frans Brüggen, Daniel Reuss, Jordi Savall, Jos van Veldhoven and Rinaldo Alessandrini. As a soloist he has performed the oratorio repertoire of J.S. Bach, Antonio Vivaldi, Reinhard Keiser, Monteverdi, Mozart and Schubert.