The Los Angeles Dodgers drafted Rooney in the third round, with the 104th overall selection, of the 2018 Major League Baseball draft.[3] He split his first professional season between the rookie-level Arizona League Dodgers and Single-A Great Lakes Loons, recording a 1.80 ERA in eight starts. Rooney split the 2019 campaign between Great Lakes and the High-A Rancho Cucamonga Quakes, accumulating a combined 10-4 record and 2.84 ERA with 89 strikeouts in 104+2⁄3 innings pitched across 20 starts.[4]
Rooney did not play in a game in 2020 due to the cancellation of the minor league season because of the COVID-19 pandemic.[5] He returned to action in 2021 with the Double-A Tulsa Drillers, compiling an 0-2 record and 4.08 ERA with 42 strikeouts across eight appearances (five starts).[6] Rooney made 24 appearances (17 starts) for Tulsa in 2022, struggling to a 4-7 record and 6.15 ERA with 99 strikeouts over 98 innings of work.[7]
In 2023, Rooney spent time with Tulsa and the Triple-A Oklahoma City Dodgers. In 53 appearances (one start) for the two affiliates, he posted a cumulative 6-3 record and 2.86 ERA with 69 strikeouts and three saves across 69+1⁄3 innings pitched.[8] Rooney made 53 appearances out of the bullpen for the Triple-A Oklahoma City Baseball Club in 2024, registering a 5-2 record and 4.33 ERA with 71 strikeouts and one save across 60+1⁄3 innings pitched. He elected free agency following the season on November 4, 2024.[9]
Miami Marlins
On November 13, 2024, Rooney signed a minor league contract with the Miami Marlins organization.[10] Rooney made 38 appearances for the Triple-A Jacksonville Jumbo Shrimp in 2025, compiling a 2-1 record and 2.45 ERA with 45 strikeouts and four saves across 33 innings of work.[11]
Houston Astros
On August 3, 2025, the Marlins traded Rooney to the Houston Astros in exchange for cash considerations; he was subsequently added to the 40-man roster and promoted him to the major leagues for the first time.[12] On August 5, he was optioned to the Triple-A Sugar Land Space Cowboys without appearing for Houston, becoming a phantom ballplayer.[13] On August 24, the Astros promoted Rooney to the major leagues for a second time.[14][15] He pitched 1+1⁄3 innings of relief but allowed a Luis Vázquez solo home run in his MLB debut in a 3–2 away loss to the Baltimore Orioles on August 24.[16] On August 26, Rooney was placed on the injured list due to left elbow inflammation.[17] He was transferred to the 60-day injured list on September 3, officially ending his season.[18] On September 23, it was announced that Rooney had undergone surgery to remove bone spurs and address tennis elbow.[19] On November 6, Rooney was removed from the 40-man roster and sent outright to Sugar Land.[20] He elected free agency the same day.[21]
Tampa Bay Rays
On November 15, 2025, Rooney signed a minor league contract with the Tampa Bay Rays.[22]
