Juventus have boosted their options ahead of the new Serie A season by completing the signing of two young players.
Masi joined Juve earlier this summer in a co-ownership deal but the Turin club have now signed him outright.
A statement on the club's official website read: "Alberto Masi is 100% a Juventus player.
"An agreement has been reached for Pro Vercelli to concede their half of his registration."
Troisi has signed a four-year contract with Juve but will spend this season on loan at Atalanta in deal involving Italian starlet Manolo Gabbiadini.
Juventus begin their title defence against Parma on Saturday, August 25.