Perez moved to the Serie A side in a loan deal which will become permanent in the summer, despite having broken into the Barca side earlier in the campaign with 12 appearances and two goals.
"For me, it was a surprise that they decided to dispense with me," the 22-year-old told EFE. "I consider that I didn't deserve that."
"Ever since the 'cadete' team (around the age of 16), I had offers to leave Barca, some of them from England.
"And even when I was at Barca B, I had offers from LaLiga teams and I always said 'no' because I wanted to get to the first team.
"Later, I had opportunities and I think I took advantage of them as much as I could. In fact, I even earned a contract as a player in the first team."
Perez featured amid a number of injuries to Barcelona's forwards at the beginning of the season, but his sale still came as something of a surprise and it was rumoured to be for financial reasons.
"Even today, I still don't understand what happened," he said. "Either the club needed the money, or there is something else which escapes me. But it's in the past now."
And the Catalan does not believe he was sold because of Ansu Fati's emergence at the same time.
"I never saw it like that," he said. "I play as an inverted winger on the right and he does the same on the left."
Despite his sadness at leaving Camp Nou, Perez says he is now in a positive mindset at his new club.
"I'm at Roma now, one of the best teams in Italy," he said. "I was worried at the time because it's hard to leave Barca and leave your family and friends.
"A lot of people say it's very cold when you leave Barca, but I believe there's a lot of life outside Barca. I'm doing really well at Roma and I'm earning myself a place."