Roberts died Thursday of natural causes at his home in Temple Terrace, Fla., the Phillies announced.
The right-hander was the most productive pitcher in the National League in the first half of the 1950s, topping the league in wins from 1952 to 1955, innings pitched from '51 to '55 and complete games from '52 to '56.
He won 286 games and put together six consecutive 20-win seasons. Roberts had 45 career shutouts, 2,357 strikeouts and a lifetime earned-run average of 3.41. He pitched 305 complete games but also holds the dubious distinction of giving up more home runs than any other Major League pitcher, with 505.
"Workhorse is a weak description," Philadelphia Daily News writer Stan Hochman wrote about Roberts in 2003. "He was a mule, stubborn, cantankerous and willing to toil from sunup to sundown."
Phillies fans will remember Roberts as the leading pitcher on the 1950 squad that won the franchise's first pennant in 35 years but lost the World Series to the New York Yankees. Roberts put together a 20-11 season with a 3.02 ERA and five shutouts.
The team, with several 25-and-younger stars, including Roberts, Richie Ashburn and Del Ennis, was dubbed the "Whiz Kids."
Roberts spent 14 of his 19 seasons in Philadelphia and was the stalwart of the rotation from 1948 to 1961. His 234 wins as a Phillie are even more impressive considering that the team lost more games than it won in that stretch. His best statistical season came in 1952, when he went 28-7 with a 2.59 ERA.
"Probably the best fastball I ever saw was Robin Roberts'," Hall of Famer Ralph Kiner said.
Roberts had a reputation as a control pitcher who relied heavily on his fastball and who threw strikes, sometimes to his detriment. He gave up only 1.3 walks per game over his career but also gave up at least 40 home runs in three straight seasons.
"I had a high fastball, and I either overpowered them or they overpowered me," he once said.
Roberts remains the Phillies' all-time leader in games pitched, complete games and innings pitched. He was the leader in wins and strikeouts until Steve Carlton eclipsed those marks.
He was elected to the Baseball Hall of Fame in 1976.
Robin Evan Roberts was born Sept. 30, 1926, in Springfield, Ill. His parents, Tom and Sarah, had moved to central Illinois from Wales in 1921. His father was a coal miner.
Roberts attended Michigan State University, where he was a star on both the basketball and baseball teams, and signed with the Phillies for $25,000 after graduating in 1947.
After retiring from baseball, Roberts was a stockbroker and served as baseball coach at the University of South Florida.
Roberts is survived by four sons, a brother, seven grandchildren and one great-grandson. His wife, Mary, died five years ago.