The Argentina winger left Juventus for Roma last week, despite also having a bumper offer from Leicester.
Soule said at his presentation today: "Leicester wanted me a lot, both the coach and the sporting director had called me to convince me of their project.
"But then I felt the affection of (coach Daniele) De Rossi, of Roma, of the teammates who supported me contacted and I decided from that moment to say no to all the other clubs and to only think about Roma for all these reasons plus one."
He continued, "The fans. They are a spectacle, and that's not just saying so. Last season Paulo (Dybala) and Leo (Paredes) invited me to the Olimpico to watch the Europa League match against Feyenoord. I entered, I heard 70 thousand people singing from the anthem to at the end of the match.
"Once I came out I told my brother that I had never seen such passionate, thrilling fans. I had already honestly thought about Roma, when I still didn't even know if I would continue at Juventus."