The 19-year-old's excellent performances for Ajax over the last two seasons saw him attract attention from Europe's top sides, with reports the likes of United and Barca heavily linked.
"I'm very satisfied with what he is doing," Kluivert told La Gazzetta dello Sport. "He doesn't speak much, but he is someone who knows how to listen and is motivated, I would have liked to stay in Ajax for another year, but he chose for himself. I think Roma is a good solution.
"A jump to the Premier League would have been difficult... I think United would have been too big a jump. Roma is an important club, but the pressures are lower.
"Roma must not win by force and it is a club that is used to good football. It is the ideal place for Justin right now. Then, who doesn't dream of Barcelona? But Italian football is catching up and Justin can take advantage of it."
After finishing third in the league and 18 points behind champions Juventus last season, Eusebio Di Francesco's team are aiming for the title this time around, and Kluivert, who recently took over as Clarence Seedorf's assistant manager at Cameroon, thinks they have a good chance.
"I hope he can win the Scudetto. Juve are the strongest, but you never know," he added. "I would like to go to Italy soon. I'm busy with the new job, but for Justin I always have time. I want to see him win with Roma. And I want to see him happy."