Arena, who earned his first team promotion with three goals in his last three games for their under-20 side, was subbed on for the returning Leon Bailey in the 80th minute of the match with his side trailing 2-1.
He needed less than two minutes to make an impact, striking for Roma with his very first touch, getting onto the end of a Wesley France cross and nodding it past Torino goalkeeper Alberto Paleari.
It wasn't a dream debut in terms of team performance, with Roma suffering a shock elimination from the Coppa Italia through a late Emirhan Ilkhan winner, but it was nonetheless an eye-catching cameo from the young Aussie.
Arena had already made Italian football history since leaving the Western Sydney Wanderers club academy in 2022 to move to Pescara, signing his first professional contract within a week of turning 16 and scoring on Serie C debut.
In doing so, Arena also eclipsed a long-time record held by former PSG and Italian national team legend Marco Verratti by becoming Pescara's youngest ever club scorer at age 16.
"I will never forget the emotion I felt after the goal," Arena said in March.
"I was a little nervous. I came on and did what I learned with the first team. I still can't believe what happened. The boys helped me a lot, even in the first seven months with them, where I learned a lot.
"I warmed up and when the coach called me, I was emotional."
Arena has played underage football for both Australia and Italy through his Italian passport and remains eligible for both nations.