Rossi, 19, spent the 2019-20 season with the Ottawa 67's of the Ontario Hockey League (OHL), totaling 120 points (39-81=120) in 56 games. He led all players in the Canadian Hockey League (OHL, QMJHL, WHL) in assists and points. The 5-foot-9, 183-pound native of Feldkirch, Austria, was named the OHL's Most Outstanding Player of the Year, just the second European import player to win the award and was named to the OHL First Team All-Star. He led the OHL with a plus-69 rating and ranked second in power-play assists (31). Rossi registered a point in 52 of 56 games played and tallied 47 points (21-26=47) during a season-best, 18-game point streak (Nov. 10-Jan. 10). He ranked second on his team in goals, third in shots (193) and fifth in power-play goals (7) and game-winning goals (5). The left-shot center was selected by Minnesota ninth overall of the 2020 NHL Entry Draft on Oct. 6. He became the second all-time Austrian-born player to be drafted by the Wild, last, Christoph Brandner in 2002 (No. 237) and became the fifth Austrian-born player selected in the first round of an NHL draft, joining former Wild player Thomas Vanek (No. 5, 2003), Michael Grabner (No. 14, 2006), Andre Burakovsky (No. 23, 2013) and Marko Dano (No. 27, 2013).
Rossi recorded 65 points (29-36=65) in 53 games with Ottawa in 2018-19. He led OHL rookies in plus/minus rating (plus-51), PPG (9) and power-play points (20), ranked second in scoring, T-2nd in GWG (5), third in assists and T-3rd in goals and shots on goal (165). He totaled 58 points (25-33=58) in 43 career games with GCK Zurich (Swiss-Jr.) over two seasons (2016-2018) and represented Austria at the 2018 IIHF World Junior Championship and the 2018 IIHF World Under-18 Championship. His father, Michael Rossi, was a defenseman who played 20 seasons of professional hockey in Austria from 1992-2011.