A Louisiana Tech graduate, Robertson played one year of professional baseball before deciding to move a different direction as he began coaching high school basketball. During his 12 years on the high school level, including eight at his alma mater of Byrd, he registered an overall mark of 163-91. Robertson was then hired by former Tech President Dr. F. Jay Taylor in 1964 where he coached the Bulldogs for 10 years, compiling a mark of 165-86. In addition to leading LA Tech three Gulf States Conference titles and two NCAA Tournament appearances, he also coached the program to a No. 1 ranking in the national college division in the early 1970s along with star forward Mike Green. Following his college stint, Robertson moved to the professional ranks where he spent more than two decades in the NBA with nine different franchises. He served as the head coach for three teams, including being the first head coach ever for the New Orleans Jazz. He also spent time as a head coach for both the Chicago Bulls and the Detroit Pistons. He was a member of the Phoenix Suns staff in 1992-93 when the franchise advanced to the NBA finals before falling to the Michael Jordan-led Chicago Bulls. Robertson also coached in two NBA All-Star games.