Hornsby is considered by many followers of baseball's history to be one of the game's greatest hitters (and perhaps its greatest right-handed hitter of all time), on a level with Ted Williams, Ty Cobb, Babe Ruth and Stan Musial. He holds the modern record for highest batting average in a season, with .424 in 1924, and won baseball's Triple Crown in 1922 and 1925. He won the NL's MVP Award twice, in 1925 and 1929. At his peak ability, from 1920 to 1925, Hornsby led his league in batting average all six years, in RBI four years, and in home runs twice. Over the 1921 through 1925 seasons, Hornsby averaged an astonishing .402 for five years, a feat unlikely to be equaled again. He hit over 300 homers in his career, not all of them as a second baseman. He is among the top four for home runs by a second baseman, as of the start of the 2005 season.

In addition to his success on the field, he was one of baseball's more talented player-managers, guiding his Cardinals to a World Series victory over Babe Ruth's New York Yankees in 1926.

Hornsby was one of the more controversial characters in baseball history. Although he did not drink or smoke, he was a compulsive gambler. As with Ty Cobb, his photogenic smile belied a dark side. One writer characterized him as "a liturgy of hatred." His chief interest was in winning, and he could be as sarcastic and uncompromising with club owners as he was with his teammates. When Hornsby was traded from the St. Louis Cardinals to the New York Giants after the 1926 season, the deal was held up because Hornsby, as part of his contract as the manager of the Cardinals (he was a player/manager at the time), owned several shares of stock in the Cardinals. Cardinals owner Sam Breadon offered Hornsby a sum for the stock considerably lower than what Hornsby demanded for it, and neither would budge. Eventually, the other owners of the National League made up the difference, and the trade went through.

As with some other star athletes, as a manager he had trouble relating to players who shared neither his talent nor his zeal for winning. As his playing skills waned, he tended to be shuffled from team to team, wearing out his welcome quickly among his charges. Having won the World Series as a player/manager with the Cardinals, he was traded to the Giants for 1927, then to the Boston Braves for 1928, and finally moved on the Chicago Cubs in 1929, where he became their player/manager (and remained for three seasons thereafter), thus playing for four different teams in four years.

As Bill Veeck related in his autobiography, Veeck as in Wreck, his father Bill Sr., who was President and General Manager of the Chicago Cubs, had hired Hornsby, and soon disposed of him when the usual problems surfaced. Some years later, when the junior Veeck hired Hornsby to manager his St. Louis Browns for a time, his widowed mother wrote him a letter asking, "What makes you think you're any smarter than your Daddy was?" After a near-mutiny by the players, Veeck let Hornsby go, and his mother wrote back, "Told ya so!" Veeck, alert as ever to an opportunity for publicity, arranged a stunt in which he was awarded a trophy by the players for freeing them from Hornsby's control.

In his later years, Hornsby's disdain for younger players only increased. According to the book Can't Anybody Here Play This Game?, Hornsby was hired by the fledgling New York Mets to scout all the major league players. His report was not especially useful, as the best compliment he could come up with for anyone was "Looks like a major league ballplayer"-his assessment of Mickey Mantle. In another anecdote, Hornsby was reviewing a group of major league players with his customary none-too-complimentary remarks. Included in the group were Chicago Cubs' third baseman Ron Santo and outfielder Billy Williams. Hornsby had just gotten through dimissing one player with the comment, "You'd better go back to shining shoes because you can't hit," when Santo whispered to Williams, "If he says that to me, I'm going to cry." When Hornsby came to Santo, he said, "You can hit in the big leagues right now," then turned to Williams and said, "So can you."

Contrasting with his usual contempt for young players, he could be generous with those who had the "right stuff". When Hornsby was managing Cincinatti, Reds players recalled him giving impromptu batting tips to the opposition, unable to help himself. Biographers of Ted Williams cite the story that the young Williams spoke with the aging Hornsby about hitting. Hornsby's secret was simply this: Wait for a good pitch to hit. That became Williams' creed and the creed of many who followed.

As Pete Rose said to a reporter in 1978 while he was pursuing a 44-game hitting streak and had just tied Hornsby's personal best at 33, "Ol' Rogers was quite a hitter, wasn't he?"

Hornsby was the great-grandson of early Texas pioneer Reuben Hornsby and is a distant relative of musician Bruce Hornsby, who sometimes performs with a bust of Rogers on his piano. His unusual first name was his mother's maiden name.

He died in 1963 of a heart attack after cataract surgery. He was buried in the Hornsby Bend cemetery east of Austin, Texas.