Rossman was born in La Habra, California, to Charles (an actor) and Denyce Rossman, has a younger brother (Spencer), and is Jewish.[2][3][4][5] He attended La Habra High School ('10), where he played baseball (batting .452 as a junior), football, and soccer (as the starting goalkeeper).[3][6]
He then attended Cerritos College in California, where Rossman played baseball and as a freshman was named a 2nd team All Star.[3] In his two seasons at Cerritos, while playing the outfield he batted .307/.446/.432 his freshman year, and .341/.459/.549 his sophomore year.[7][8][9]
Rossman was selected in the 22nd round of the 2014 Major League Baseball draft by the Los Angeles Dodgers, as a pitcher.[11][12] While he "definitely did not want to be a pitcher ... I wanted to be an outfielder in the big leagues," and several teams were interested in him as an outfielder, the Dodgers insisted that he transition to pitcher.[13] In 2014 as a relief pitcher for the rookie-level AZL Dodgers, he was 0-2 with one save and a 4.74 ERA in 19 innings, with 23 strikeouts.[14] In 2015 with the Single-A Great Lakes Loons he was 3-1 with 4 saves and a 2.26 ERA in 51.2 innings over 29 games, in which he had 54 strikeouts.[14] In 2016 pitching all but one inning for the High-A Rancho Cucamonga Quakes, he was 4-0 with a 3.43 ERA in 39.1 innings over 23 games, in which he had 34 strikeouts.[14]
He was slow to recover from a triceps injury, which impeded his velocity. Rossman was released by the Dodgers on August 30, 2016.[13][15][11]
On June 18, 2017, Rossman signed with the Sioux City Explorers of the American Association of Professional Baseball.[16] He made 20 appearances for the team, posting an 0-2 record and 4.54 ERA with 30 strikeouts and 1 save in 35.2 innings pitched. On February 5, 2018, Rossman was released.[17]
On April 1, 2019, after not playing in the 2018 season, Rossman signed with the Cleburne Railroaders of the American Association of Professional Baseball.[18] Pitching in 6 games for Cleburne, he posted a 1-0 record and 5.40 ERA with 10 strikeouts in 6.2 innings pitched. He was released on June 11.
Rossman spent the remainder of the 2019 season with the Trois-Rivières Aigles of the Canadian-American Association. In 29 appearances, he registered a 3-0 record and 2.41 ERA with 48 strikeouts in 33.2 innings of work. During the season, Rossman also became vegan.[19]
Following the 2019 season, the Can-Am Association announced it would be merging with the Frontier League for the 2020 season, but play was delayed until 2021 due to the COVID-19 pandemic.[20] Rossman would spend 2020 with the Nerds Herd in the City of Champions Cup league, logging a 3.60 ERA with 23 strikeouts in 15 appearances.[21]
On November 9, 2021, Rossman signed a minor league contract with the Philadelphia Phillies organization, at which point he was throwing his fastball in the high 90s, and touching 99 mph, along with an 88 mph slider.[24][25][12] He was assigned to the Double-AReading Fightin Phils at the beginning of the season, and before he was called up he pitched in 27 games (including 8 starts; the first of his professional career), with a 3.32 ERA in 40.2 innings in which he struck out 48 batters.[26][27][28]
Rossman was promoted to the Phillies major league roster on July 13, 2022.[29] He made his MLB debut that day, at 30 years of age, after five years out of affiliated minor league baseball.[27][30] Pitching the 8th inning that evening against the Toronto Blue Jays, he first walked a batter and gave up a home run to Teoscar Hernandez.[1] He then retired the next three batters on only nine pitches, however, including a 98 mph four-seam fastball to strike out Matt Chapman.[1] After the game, he was sent back to the minor leagues.[1] In 2022, with Reading he was 2-2 with one save and a 3.02 ERA in 29 games (9 starts) in which he pitched 44.2 innings allowed 29 hits, and struck out 56 batters.[31] With the Triple-A Lehigh Valley IronPigs he was 3=3 with a 6.04 ERA in 15 games (5 starts) in which he pitched 25.1 innings and struck out 27 batters.[31] While he had pitched in only one game for the Phillies, he was awarded a World Series ring.[32] He elected free agency following the season on November 10.[33]
On March 22, 2023, Rossman signed a minor league contract with the New York Mets organization.[34] He was assigned to the Triple-A Syracuse Mets to begin the season.[35] In 18 games for Syracuse, he struggled to an 8.18 ERA with 20 strikeouts in 22.0 innings of work.[36]
Rossman pitched for Team Israel in the 2023 European Baseball Championship in September 2023 in the Czech Republic, and was 0-0 with one save and a 0.00 ERA in which he held batters hitless with seven strikeouts over four innings across two games.[48]