
Rosario finished the 2021 season batting. It included two home runs, one being the first inside-the-park home run in his career. On August 31 against the Kansas City Royals, Rosario went 5-for-5 with a career-high 5 RBIs. Around that same time, Rosario became the team's regular starting shortstop. Giménez was demoted to the minors on May 18. Rosario's only prior experience in the outfield was three innings spent in left field with the Mets in 2019. During Rosario's first three innings in the outfield during a spring training game, he committed three errors which led to eight unearned runs being scored. In March 2021, the Indians began transitioning Rosario into a role as an outfielder with the help of coach Kyle Hudson, implicitly giving the starting shortstop job to Giménez. On January 7, 2021, the Mets traded Rosario, Andrés Giménez, Josh Wolf, and Isaiah Greene to the Cleveland Indians for Francisco Lindor and Carlos Carrasco. Louis Perfectos against the Cleveland Spiders in 1899. It was the first time a visiting player had hit a walk-off home run since Ed McKean hit one for the St. The Mets were the home team because they were making up for a previously cancelled game. On August 28, 2020, Rosario hit a walk-off home run against the New York Yankees at Yankee Stadium. However, Rosario led the National League in singles. On defense in 2019, he had -10 Defensive Runs Saved (DRS), the worst in the National League among qualifying shortstops. He had the lowest pull percentage of all NL batters (30.4%). 287/.323/.432 with 15 home runs and 72 RBIs, and while he stole 19 bases he tied for the major league lead in caught stolen with 10. He had his first career multi-home run game on May 20, 2018, hitting two home runs against the Arizona Diamondbacks. On August 11, 2017, Rosario hit his first career Major League home run off of Héctor Neris.

In that game, Rosario recorded his first career Major League hit off of Scott Oberg. Rosario made his MLB debut on Augagainst the Colorado Rockies at Coors Field. Rosario earned Pacific Coast League All-Star honors as well as being awarded the 2017 PCL Rookie of the Year. Rosario was named to the Triple-A All-Star Game and the All-Star Futures Game for 2017.

In April 2017, Rosario was declared the top prospect in baseball by writer Keith Law. Rosario was assigned to the Las Vegas 51s of the Class AAA Pacific Coast League to start the 2017 season. The Mets added Rosario to their 40-man roster after the 2016 season. Rosario before the 2016 All-Star Futures Game
