Belloni was introduced as a late substitute and, despite defeat, he was impressed with the attitude shown by his teammates.
"I'm happy to make my debut," he told Inter's official website. "To play on this pitch that has hosted so many champions is something truly incredible. However, I'm sorry about the result and our elimination.
"What struck me about the Inter players? The desire, commitment and determination they always show, in every training session and every match."
Roma advanced 5-3 on aggregate and will meet Lazio in May's final.