Robert, the youngest of nine children born to Albert and Janette Allen in Houma, Louisiana, graduated from South Terrebonne High School in 1987.
In 1988 he moved to Los Angeles where he struggled to find work, lived in a car and became a part of the "Tent City" community of homeless.
After missing out on a spot on the 1992 United States Olympic boxing team by losing to Raúl Márquez in the Trials, Allen turned professional in 1993.
The first fight ended in a no contest when Hopkins was pushed out of the ring by referee Mills Lane when he was breaking a clinch.
A father of four, Allen would work as a trainer at the Paul Murphy Boxing Club in Atlanta, Georgia after retiring.