Roosevelt was born as Kenneth Stanhope Sanderson in Meeker in Rio Blanco County in northwestern Colorado. He was an athlete and a cowboy in his youth. He started performing as a stuntman in 1916, his first work being on the film Hell's Hinges. He continued working as a stuntman as well as an actor throughout his long Hollywood career. Roosevelt served in the United States Navy during World War I. Although it has been said that he served aboard the USS Norfolk, and that it was sunk during that war, no record of a USS Norfolk being in service during World War I has been found.
Following the end of World War I he returned to Hollywood, performing stunts in films as notable as The Sheik, the 1921 movie classic starring Rudolph Valentino and for which Valentino would become most remembered. Roosevelt's first acting role was in the 1924 film Down in Texas. He would star in 37 films from 1924-1929, most of which were western films. He made a successful transition to "talking films", mainly because of his abilities as a stuntsman.
In 1930, he appeared alongside William Haines and Leila Hyams in Way Out West, which continued him on the path of western film roles, mostly in B-movies. During the 1930s he appeared in 66 films—some in which he both acted and did stunt work—almost all being westerns, and appeared with such notable actors and actresses as Harry Carey, Hoot Gibson, Gloria Stuart, Joel McCrea, Edward G. Robinson, Bette Davis and Humphrey Bogart. In 1939 he both performed stunts and had a minor role in the Claire Trevor-John Wayne classic Stagecoach, and in 1940 he appeared, uncredited, again with John Wayne in The Man from Dakota, in which he also performed stunts. Throughout the 1940s he both appeared in or performed stunts in 32 films, most notably alongside Randolph Scott and Lloyd Bridges in Abilene Town.
From 1950 through 1962 he appeared in or perform stunts in thirty-six films and two television series. He retired after 1962 with his last appearance being uncredited in the John Wayne and James Stewart film The Man Who Shot Liberty Valance. He returned home to Meeker, Colorado, where he was living at the time of his death on October 6, 1973, at the age of seventy-five.
- "Full Cast and Crew for The Life and Legend of Wyatt Earp". Internet Movie Data Base. Retrieved January 23, 2013.