Rosengarten lettered in both football and basketball at Valor High School in Colorado. He played on both the offensive and defensive lines and amassed over 100 tackles in 48 games. He was a consensus 4-star recruit and 247Sports had him listed as the no. 1 prospect in Colorado. He committed to Washington over several Division 1 offers.
In 2020, as a true freshman, Rosengarten only saw action in one game for Washington. During the 2021 season, he played in 4 games and maintained a year of eligibility. Last season, Rosengarten earned a starting role at the right tackle position and played well enough to be named All-Pac 12 third team. He was named to the Freshman All-America First Team by the FWAA.
This season, Rosengarten started every game for the Huskies and has declared for the 2024 draft, foregoing the remainder of his eligibility.