As their popularity increased, they received offers to appear in movies with Gene Autry, Dick Foran, Bing Crosby, and Charles Starrett. Roy auditioned for the role of a singing cowboy at Universal but lost out to a young man named Leland Weed, who starred briefly in B-Westerns as Bob Baker. Later, he heard that Republic was searching for a new singing cowboy star, to give their own Gene Autry some competition. Roy sneaked into the studio and ran into Sol Siegel, who remembered him from his appearances in the Autry films. Siegel arranged an audition and young Slye, then 26, was soon signed to a contract for $75.00 per week. Roy never had an acting or singing lesson, but he worked hard at becoming the best singing cowboy he could possibly be. He rented a horse and spent many hours in the saddle, learning how to make himself look like he was born on the range. He got a pair of six-shooters and practiced everything there was to know about handling a gun - twirling, spinning, shooting, and practicing his fast draw.

Roy's first starring film was released in 1938, Under Western Stars, which became an instant hit. From 1943 through 1954, (the last year the survey was made,) Roy was the number one ranked Cowboy Star, based on box office receipts. For a few years, he ranked in the top ten for all movie stars! His career was unparalleled by virtually any other entertainer. In addition to his movies being number one, his television shows were among the highest rated of their time, his records topped the charts, he set personal appearance attendance records and he was a one man industry with his name and likeness on hundreds of products from cookies to toys to clothing.

Roy's films were based on a formula that included action, romance, and comedy, they had something for everyone. His pictures contained some of the most innovative action sequences ever recorded on film, a testament to the skilled directors, cameramen, stuntmen, and special effects people at Republic. They were the best in the business and they took a lot of pride in their work. None of the major studios at that time could even come close to capturing on film the exciting action that was a part of every Rogers film. The musical production numbers in some of his films rivaled those of MGM. If they had been filmed in Technicolor, they would have indeed been spectacular.