Rock was born at Southsea in April 1957. He was educated at The Portsmouth Grammar School.[1] He began his association with Hampshire in 1974, initially playing in the Second XI Championship.[1] He made his debut in first-class cricket for Hampshire against Surrey at The Oval in the 1976 County Championship, with him making two further Championship appearances that season.[2] He established himself in the Hampshire side in the 1977 County Championship, making eleven appearances;[2] during this season, he scored his maiden first-class century with 114 runs against Leicestershire,[1] sharing in a partnership of 124 for the opening wicket with Gordon Greenidge.[3] Later in the season at Basingstoke, he scored a second century against Nottinghamshire.[1] In that same season, he also made his debut in List A one-day cricket against Somerset at Street in the John Player League, with Rock making nine one-day appearances throughout the season, which included two matches in the Gillette Cup.[4]
Rock was unable to replicate his form during the 1978 season, and was dropped from the County Championship team early in the season.[5] He returned to the Hampshire side against the touring Pakistanis, following injuries and the unavailability of regular players,[6] Alongside seven first-class appearances in 1978,[2] Rock also made four one-day appearances in the John Player League,[4] a tournament which Hampshire won. He appeared more regularly for Hampshire in 1979, making sixteen first-class and five one-day appearances;[2][4] in first-class cricket that season, he scored 473 runs at an average of 18.19,[7] making one century against Warwickshire at Nuneaton.[1] Following the 1979 season, Rock returned to Hampshire for pre-season preparation ahead of the 1980 season, but retired before the start of that season.[1] In 37 first-class matches, he scored 1,227 runs at an average of 19.17.[8] In eighteen one-day matches, he scored 286 runs at an average of 19.06, with two half centuries and a highest score of 68.[9]