2009-10: Rocco Grimaldi split the season between the U.S. NTDP national team and the squad playing in the USHL. In 32 USHL games, he scored 11 goals and added 9 assists for 20 points. In 36 games for the Under-17 squad, Grimaldi scored 14 goals and added 26 assists for 40 points. In 26 games for the Under-18 squad, he scored 7 goals and added 16 assists for 23 points. Grimaldi played for the gold medal USA squad at the 2010 World Under-17 Hockey Challenge, scoring 4 goals and adding 10 assists for 14 points in 6 games. His performance earned him a berth on the tournament All-Star Team. Grimaldi also earned gold for the USA at the 2010 U-18 World Junior Championship, where he scored 2 goals and added 8 assists for 10 points in 7 games.
2010-11: In 23 games for the NTDP squad playing in the USHL, Grimaldi scored 12 goals and added 13 assists for 25 points. He won a gold medal again while playing for the USA at the 2011 U-18 World Junior Championship, scoring 2 goals and adding 6 assists for 8 points in 6 games.
2011-12: Grimaldi appeared in just four games for the University of North Dakota in what would have been his freshman year. A knee injury suffered in pre-season camp eventually led to season-ending surgery in January 2012. In four early season games with the Fighting Sioux he had 1 goal with 1 assist and was minus-five with 2 penalty minutes. He was invited to USA Hockey's Lake Placid U20 Evaluation Camp but was still recovering. Grimaldi was granted a medical redshirt by the NCAA and will once again be a freshman in 2012-13.
2012-13: Grimaldi made a smooth return from the knee injury of the previous season — finishing as North Dakota's third-leading scorer as a redshirt freshman and winning a gold medal with the USA at the 2013 World Junior Championship. Skating with several different line mates for the Fighting Sioux, he scored 13 goals with 23 assists and was +14 with 18 penalty minutes in 40 games. North Dakota finished third in the WCHA and after an overtime loss to Colorado College in the WCHA semifinals defeated Niagara before falling to eventual national champion Yale in the West Region final. Grimaldi scored 2 goals with 2 assists and was +4 with 4 penalty minutes in seven games at the WJC. The USA defeated Sweden, 3-1, in the gold medal game.
Grimaldi is a top-flight NHL hockey player in a small package. He is a terrific skater, both with and without the puck. His quickness and acceleration are truly high end and he has the agility to match. His shot is deadly, and his passing skills are professional grade. He is a tireless worker and often the most competitive player on the ice. He combination of puck skills, compete level and explosive skating give him everything he needs to overcome any issues he might have because of his size.
Grimaldi will play another season for North Dakota, but it could well be his last. He was perhaps the best player at the recent Panthers development camp, and looks ready to take the next step. His linemates for the Sioux—Corban Knight (CGY) and Danny Kristo (NYR)—have both left the program, so Grimaldi will be counted on to lead the team and provide offense. Although he has been progressing well, he remains a prototypical boom-or-bust prospect whose NHL career will be as a scoring-line playmaker and sniper or nothing at all.