Rosario made his major league debut on May 6, 2015. Leading off the bottom of the 3rd inning, Rosario swung at the first pitch he saw from Oakland Athletics starter Scott Kazmir, and hit an opposite-field home run, becoming the 115th player in major league history to hit a home run in his first at-bat. Rosario played in 122 games for the Twins, sharing outfield duties with Torii Hunter, Aaron Hicks, and fellow prospect Byron Buxton. Despite being called up a month into the season, Rosario led all of baseball in triples with 15, and was second in outfield assists with 16, just one behind Avisail García of the Chicago White Sox. Rosario finished his rookie campaign with a.267 batting average and 13 home runs.
2016
With the retirement of Torii Hunter and the Twins' trade of Aaron Hicks, Rosario entered 2016 as the Twins' projected everyday left fielder. After a slow start and the emergence of both Robbie Grossman and Max Kepler, Rosario saw his playing time dwindle ultimately leading to his demotion to Triple-A. He was brought back up towards the end of the season, and finished the year with a.269 batting average, 10 home runs, and 32 RBI in 92 games played.
2017
In 2017, Rosario became the Twins’ everyday left fielder and emerged into one of the AL’s best hitters. On June 13 he had his first career 3 home run game going 4-5 and driving in 5 runs. Later in the season he won his first Player of the Week for the week of August 13, going.444/.484/1.000 with 4 home runs. He ranked in the top 25 for batting average, OPS, slugging, and doubles. In 151 games he batted.290 with 27 home runs and 78 RBI.
2018
On April 18, 2018, before a sold-out crowd at the Hiram Bithorn Stadium in his homeland Puerto Rico, Rosario scored the winning run in the bottom of the 16th inning, coming around on Ryan LaMarre’s single that gave Minnesota a 2-1 win over the Cleveland Indians. Rosario had a 3 home run game for the second time in his career on June 3 against the Cleveland Indians, going 3-5 driving in 4 runs while hitting the game winning walk-off home run. He finished the season with the lowest fielding percentage among major league left fielders, at.967, and batted.288 with 24 home runs, 77 RBI, and a career high 161 hits in 138 games. Rosario was considered an All-Star "snub" in 2018.
2019
In 2019 he batted.276/.300/.500. He swung at the highest percentage of all pitches of all American League batters.
