Mastromanno served as Florida State's main punter as a freshman in 2020, recording an average of 43.5 yards per punt which ranked seventh in the Atlantic Coast Conference (ACC) and 33rd nationally.[8] He remained the starter in 2021, playing in 12 games and being chosen fourth-team All-ACC and FSU's special teams MVP after averaging 42.7 yards per punt with 18 punts inside the 20 and a long of 65 yards.[9] In 2022, he punted 34 times with an average of 41.8 yards per punt, having a long of 53 and five punts of over 50 yards.[6]
In 2023, Mastromanno averaged 45.5 yards per punt, placing second in the ACC and 15th nationally.[10] He was named second-team All-ACC, second-team All-American and a finalist for the Ray Guy Award for best punter nationally, being FSU's first-ever finalist for the award.[3][10] He returned for a final season in 2024 and broke the ACC record and ranked first nationally with an average of 49.3 yards per punt, being named first-team All-ACC and a finalist for the Ray Guy Award.[11] He was also named a first-team All-American.[12]