Born at Side 4 in UC 0045, Greenwood was of German descent (his family's original name was "Grunwald"). Roy graduated from the Moore branch of a Earth Federation comprehensive university in U.C. 0067. In 0078, following the accidental death of his wife Katie, this father of two moved to the Zeon Dukedom and enlisted in the armed forces. As a member of the Mobile Assault Force's 1st Mobile Infantry Division, he participated in Operation British and lost his left eye for his trouble. He missed the Loum campaign while recuperating, and then returned to duty as a member of the Earth Attack Force's 5th Terrestrial Mobile Division.
Deployed in North Africa, Greenwood commanded the 5th Terrestrial Mobile Division's 1st Mobile Suit Battalion, A Platoon - also known as the Karakal unit, of Zaku Desert Type fame. He was stationed at the Alexandria base until the end of the One Year War. His subsequent whereabouts are unknown; guerrilla warfare continued in North Africa for some time after the end of the war, but it's not clear whether Greenwood (or any of the other 5th Terrestrial Mobile Division aces) participated. At the end of the One Year War, Roy was considered missing in action.