Thomas Roberts, the labor arbitrator best known for finding Major League Baseball owners guilty of colluding to prevent the movement of free-agent players after the 1985 season, died February 13. He was 84.

Roberts became a national figure in 1983 when he ruled that then-Dodgers pitcher Fernando Valenzuela could earn $1 million for a year’s salary. Valenzuela became the first baseball player to break the $1 million salary barrier through arbitration.

In 1988, Roberts awarded $10.5 million to 139 players after he found that owners had conspired to restrict the movement of free agents during the 1985 season.

The owners agreed in 1990 to settle the collusion cases for a $280-million payment. The Major League Baseball Players Association hired Roberts to oversee the distribution of the money to about 840 players.

Donald Fehr, executive director of the players association said Roberts had an “extraordinary reputation.”

“He had a really good sense of what the right and what the appropriate result should be,” Mr. Fehr said. “He was courteous almost to the point of being courtly.”

In a 1989 article in Florida’s St. Petersburg Times, Roberts said that there “is a feeling that arbitrators have a tendency to split things, to give one to the club and the next to the player in the hope of not offending either party so he’ll be hired again.”

“That’s an illusion,” he said. “A successful arbitrator doesn’t pay attention to his box score, in baseball or anywhere else.”

Only a small part of Roberts’s caseload revolved around baseball, and the arbitrator of 50 years sat in on disputes in the entertainment, broadcasting, manufacturing and airline industries.

From 1987 through 2000, Roberts mediated between General Motors Corp. and the United Auto Workers during their national collective bargaining agreement.