Later career
In 1970 he had the lead playing a US Army Major in the Japanese film Aru heishi no kake.
Robertson guest-starred as himself in the episode "Little Orphan Airplane" of The Six Million Dollar Man in 1974.
He portrayed legendary FBI agent Melvin Purvis in two made-for-television movies Melvin Purvis: G-Man (1974) and The Kansas City Massacre (1975).
In 1981, Robertson was in the original starring cast of Dynasty, playing Walter Lankershim, a character who disappeared after the first season. Robertson also played Frank Crutcher in five episodes of the TV series Dallas during the 1982–83 season.
In 1983, Robertson made Big John, another television pilot, where he played a Georgia sheriff who becomes a New York Police Department detective. From 1987 to 1988, he starred as the title character the detective series J.J. Starbuck.
Robertson played a central part in a two-part episode of Murder, She Wrote with Angela Lansbury. He was not credited in either appearance because he took issue with the show's protocol of naming all guest stars alphabetically with no exception. When the show's producers would not waver on this subject, he asked not to be credited.
In December 1993 and January 1994, Robertson appeared in three episodes of Harts of the West in the role of Zeke Terrell, which would be the final credited roles of his career.
He received the Golden Boot Award in 1985, has a star on the Hollywood Walk of Fame, and is also in the Hall of Great Western Performers and the National Cowboy & Western Heritage Museum in Oklahoma City.
In 1999, Robertson won the award for film and television from the American Cowboy Culture Association in Lubbock, Texas.
In the last few years before his death, Robertson hosted a radio program called Little Known Facts, which was broadcast on 400 radio stations.
During the 27th Annual Texas Trail of Fame Awards held October 24, 2024, Robertson was awarded a bronze star on the walkway located in the Stockyards at Fort Worth, Texas.
