In 1941 she starred with Sonja Henie and John Payne in "Sun Valley Serenade", while under contract to 20th Century-Fox. She returned to Republic Pictures in 1944, and stayed under contract there until 1948. She starred with Gene Autry in "Sioux City Sue" in 1946, and appeared in two more films with Autry: "Robin Hood of Texas" and "Saddle Pals", as well as three films with Roy Rogers, and one with Monte Hale. (Johnny D. Boggs, in his book, "Billy the Kid on Film, 1911-2012", wrote, "Lynne Roberts would co-star with Rogers in eight Westerns, billed as Mary Hart in the first seven of those.")