Best known for his defense, the 6'4" Robertson played for ten years after being selected by the San Antonio Spurs with the seventh pick in the 1984 NBA draft out of Crowder Junior College and the University of Arkansas.

[8] He would continue to be a premier defender on the Bucks, leading the league in steal percentage, an advanced metric, each of his three full seasons.

During the 1993–94 season, the Detroit Pistons traded Robertson to the Denver Nuggets in exchange for Mark Macon and Marcus Liberty.

Ed Pinckney won the franchise's opening tip-off against the New Jersey Nets, Robertson hit a three-pointer, and the Raptors were ahead 3–0.

Robertson is the father of Tyrell Johnson, 2008 NFL 2nd round draft choice of the Minnesota Vikings.

In August 1997, he pleaded no contest to four misdemeanor charges of abusing a former girlfriend and was sentenced to one year in prison.

[15] During the trial he was accused of having kicked in an apartment door while his former girlfriend and her 8-year-old daughter were inside, then taking her wallet and knocking over a television set.

Robertson allegedly returned a few hours later and ripped rings off her fingers, tore a watch off her wrist, slashed furniture, damaged clothing and tried to set a fire.