Colonel Roy Campbell is voiced by Paul Eiding and Takesho Aono in the English and Japanese versions of the games in the Metal Gear Solid series, respectively. He is also in Super Smash Bros. Brawl as a codec when you fight as Solid Snake in Shadow Moses Island; he'll talk about the various characters during the battle like Mario, Luigi and Solid Snake.
In terms of story, he made his first appearance in Metal Gear Solid: Portable Ops, where he met Big Boss in a prison cell and helped him destroy Metal Gear RAXA. Afterwards they created Foxhound, which ended up rebelling due to Big Boss's leadership. After Solid Snake killed Big Boss, Campbell became the head of Foxhound, and he later called Solid Snake to stop the uprising at Zanzibar Land.
Metal Gear Solid
After their mission was finished Campbell left Foxhound. During the incident at Shadow Moses he was taken out of retirement and forced Snake out of retirement to stop the rebellion of their old Foxhound unit, led by Liquid Snake. Campbell was forced to keep many secrets from Snake during the mission in order to save his niece Meryl (later revealed to be his daughter), who was purposely sent to Shadow Moses by the Pentagon and is now a hostage in Shadow Moses. Near the end of the mission Campbell reveals what is really going on. After Shadow Moses, Campbell went back into retirement.
Metal Gear Solid 4
In the events of MGS4 Campbell asks Snake for a personal favor and that is to kill Liquid Ocelot before he can turn the entire world into a war zone. During this mission it is revealed that Campbell is married to Raiden 's ex-wife and has a child with him; Meryl is disgusted by this and won't speak to him anymore. After Snake defeats Liquid Ocelot and stops The Patriots, Col. Campbell attends Meryl's wedding and they make amends after many years of silence.