Bianda moves to Roma for €6m.
“I'm sure this is the right choice for me, for my progression and for this next stage of my career."
Bianda has signed a five-year contract with the Giallorossi that runs until 30 June 2023 and will wear the Number 28 shirt.
“With the signing of William, Roma continues its investment in young talent," said sporting director Monchi.
“We are certain that, with the help of our coaches and our experienced players, William will continue to improve and realise his potential."