The 19-year-old Republic of Ireland international departs the Amex Stadium after making 80 appearances for the Seagulls, scoring 17 goals. Ferguson spent the second half of last season on loan at West Ham United but struggled for consistent game time due to recurring injury setbacks.
Brighton head coach Fabian Hurzeler believes the move to Rome presents a fresh opportunity for the highly rated forward to rediscover form and fitness.
"Evan had a challenging period across the past season and a half, and it has been one disrupted by niggling injury issues, which hasn't allowed him a run of games," Hurzeler said.
"He is over those injuries and has come back in great shape. Now he really wants to play regularly. This is an exciting opportunity in a strong league and with the prospect of European football."
Hurzeler confirmed that the club will be monitoring Ferguson's progress closely during his time in Italy.
"We wish Evan well for the season ahead and will be watching his progress closely throughout the season," he added.
Ferguson will now look to make an impact in Serie A as he aims to reignite his development at one of Italy's most storied clubs - and potentially earn a permanent move to the Stadio Olimpico.
Joao Felix looks poised to become the latest high-profile name to join the Saudi Pro League, with Al-Nassr nearing a 44 million pounds agreement to sign the Portuguese forward from Chelsea.
Leeds United have added further steel between the sticks with the signing of Brazilian goalkeeper Lucas Perri from Lyon, marking their seventh addition of a busy transfer window.
Yoane Wissa's future at Brentford has been thrown into doubt after the forward reportedly threatened not to play for the club again if he is denied a move to Newcastle.
Arsenal have completed the signing of Sweden international Viktor Gyokeres from Sporting CP in a deal worth 63 million euros, plus an additional 10 million euros in performance-related add-ons.
