The Barcelona-owned forward is joining Milan on-loan for the season.
"I am already in Milan and tomorrow I will be presented as an A.C. Milan player!!" wrote Bojan on his Facebook page.
"I am ready for anything and can't wait to play my first game..!! Thank you to everyone for the welcome and the birthday wishes. : ) We'll see each other tomorrow!! Forza Milan!
"I also wanted to specially thank the Roma fans for their support and affection from my first day.
"It was a great honour to defend this jersey and I wish you the best, my friends. I hug you all and will always keep you in my heart! Bojan."