The elite quarterback had originally not planned on going, citing summer workouts for Bosco, but told FOX Sports NEXT that receivers coach Tee Martin -- who recruits St. John Bosco -- convinced him Tuesday night to stop by in the morning.
Rosen said "The camp was fun," but noted his frustration when he got "blindsided in team with no pads...that was frustrating."
Rosen said two of his targets at camp Wednesday morning included Long Beach (Calif.) Cabrillo receiver Rahshead Johnson -- who is currently committed to Washington and Ventura (Calif.) St. Bonaventure tight end Bryce Dixon, amongst others.
The 6-foot-3 195-pound quarterback left campus without an offer from the Trojans but is all but certain one is on the way, it's just a matter of when.
"[USC coaches] have a big recruiting meeting right now," Rosen said. "[Quarterbacks coach Clay] Helton says they will offer me, he is just lobbying for it to happen now."
Rosen boasts well over a 4.0 GPA at Bosco. It's widely understood academics will play a large role in his college decision. He says USC fits the bill of a school he'll consider academically, "It's a great school that has churned out plenty of world class graduates," he said.