Rosnow began his lacrosse career in Seattle, playing for both the Overlake School and the Seattle Starz. After his high school career, he went on to play four years at Oberlin College as a midfielder and face-off specialist. Serving as a captain his senior year, he graduated with honors and a physics degree in 2017. With several college accolades to his name (All-NCAC First Team, All-NCAC Second team, All-Region West First Team, and NCAC Honor Roll), Rosnow began his coaching career directly after graduating with several Seattle Starz teams, coaching face-offs across all age groups as well.

After moving to Tokyo, Japan in 2017, Rosnow secured a job in the engineering and R&D department of Tecdia, where he began playing for a local club team. He was later invited to play with the Japanese National Team, and represented Japan in the 2018 World Championships in Israel. Japan finished 6th out of 46 teams in the division, and will compete against the United States, Canada, Iroquois, Australia, and England in four years. In a later tournament, Rosnow was selected as the Team Japan MVP.

At the start of 2019, Rosnow became and assistant coach at CU Boulder for their D1 lacrosse team, focusing on wing and face-off specialties. His team was ranked 7th in the MCLA and advanced to the national tournament. Additionally, during his time in Denver, he played for the Denver Outlaws of the MLL as a face-off specialist to help his team clinch a playoff spot. After working at Boulder and playing for the Outlaws, Rosnow moved to Pittsburgh and is now pursuing a masters of science degree in Information Science at the University of Pittsburgh School of Computing and Information.

“Thank you to Coach Dodson for bringing me on board,” Rosnow said. "I look forward to sharing my experiences with the players. It is my goal to help Coach Dodson and the rest of the coaching staff better the team on the field and develop skills that will translate in the classroom and their professional careers. I am excited to get started."