Roscoe actively assumed the role of Captain America after Steve Rogers abandoned the identity to become Nomad. At least two other men, Bob Russo and "Scar" Turpin, had briefly assumed the identity only to fail miserably on their respective first outings. Roscoe was a lifelong Cap fan who wanted to continue the legacy of his idol. He proved himself a competent combatant and won the approval of Rogers.
He was given the indestructible shield that went with his new identity. Falcon offered to give him further training. However Roscoe was killed in his first encounter with the Red Skull. He was tortured and crucified. Red Skull left the message that this would be the fate reserved for any other "fake" Captain Americas that dared face him. Rogers chose to reclaim the identity to defeat the Skull.