Roundtree started his professional career around 1963, as he began working as a model at the
Ebony Fashion Fair after being scouted by
Eunice W. Johnson; and
Salem cigarettes. In 1967, Roundtree joined the
Negro Ensemble Company: he then went on to play his first theatrical role by portraying boxer
Jack Johnson in the company's production of
The Great White Hope. at
St. Mark's Playhouse in 1969, directed by
Shauneille Perry. in the
CBS-TV television series (1973) Roundtree made his first big-screen appearance by playing a minor role in the film
What Do You Say to a Naked Lady?, a 1970 American hidden-camera style reality film directed by
Candid Camera creator
Allen Funt. In 1984, he starred again as a private detective, Diehl Swift, in the buddy-crime comedy movie
City Heat, acting alongside
Clint Eastwood and
Burt Reynolds. On television, he played the slave Sam Bennett in the 1977 television mini-series
Roots, and then starred as Dr. Daniel Reubens in the soap opera
Generations from 1989 to 1991. During that same period of time, Roundtree kept featuring in TV series: In 1995, he acted in
David Fincher's critically-acclaimed movie
Seven; In 1997, he appeared in the comedy movie
George of the Jungle; around the same year, he played a leading role as Phil Thomas in the
Fox ensemble drama,
413 Hope St; He served as a voice actor for the title character from the
PlayStation game
Akuji the Heartless, which was first released in 1999. In 2004, Roundtree guest-starred in several episodes of the
first season of
Desperate Housewives as an amoral private detective; Starting from the same year, Roundtree appeared in the television series
The Closer as retired
colonel D. B. Walter; in 2006, he starred in the science fiction drama series
Heroes as Charles Deveaux, the terminally ill father of main character
Simone Deveaux (
Tawny Cypress). During the same year, he also appeared in the TV series
Knight Rider as the father of
FBI agent Carrie Ravai (
Sydney Tamiia Poitier). Starting from 2013, he co-starred as the father of lead character Mary Jane Paul (
Gabrielle Union) in the drama series
Being Mary Jane, aired on
BET. In 2019, Roundtree co-starred in the comedy film
What Men Want, Roundtree's final film to be released in his lifetime was
Moving On (2023) with
Jane Fonda. The last film released was
Thelma (2024). ==Personal life, health problems, and death==