Rokuro "Rock" Okajima was a former salary-man before joining the Lagoon Company pirates in the South-Asian Seas.
His first appearance was in Black Lagoon Volume 1 CH. 0 "Black Lagoon", and his first anime appearance was in Black lagoon - Episode 1 "The Black Lagoon". His character in the Japanese series is voiced by Daisuke Namikawa, and the U.S. dub produced by Ocean Group is done by Brad Swaile.
He once worked as a salaryman under Asahi Industries, until he was abducted by the Black Lagoon company whilst on a mission. Although initially fearful of them, he eventually relented to joining them after his manager abandoned him due to his unwilling involvement in a smuggling operation carried out by Black Lagoon, and adopted the nickname "Rock" In place of his real name, Okajima Rokuro.
Unlike most of the company, Rock is in charge of most of the paper work and non-combat operations, such as linguistics and accounting. He's fluent in several languages, such as English, Spanish, and German, and is quite competent with these non-combat jobs, due to his previous experience as a salaryman. However, when provoked, Rock can become one of the most dangerous and fearsome members of the Black Lagoon company.