Robert Jens Rock (born April 19, 1954) is a Canadian musician and record producer. He played guitar in a band called The Payola$ until they broke up in 1988 (they have since reunited). He was producer for bands such as Mötley Crüe, Aerosmith, The Cult, Bon Jovi, Skid Row, and most notably, Metallica. He was also producer for David Lee Roth.