Seydou Doumbia sealed his move to Roma after the Serie A club secured his services from CSKA Moscow 14.4 million euros.
Doumbia, who is currently at the African Nations Cup with Ivory Coast, signed a new contract until June 2019.
In November, Doumbia starred in a Champions League match at Manchester City, scoring both goals in CSKA's shock win.
The 27-year-old forward wrote a message to CSKA fans on Instagram:
Una foto pubblicata da Doumbia Seydou (@doumbiaseydou) in data:
England's Tottenham and Liverpool were also reportedly interested in signing Doumbia, but his agent Jean Bernard Beytrison explained the players' choice.
"I don't know when the two clubs were first in contact, but with us it was 7-10 days ago," Beytrison told calciomercato.it. "Rudi Garcia called not to convince him, but to explain his style of football. There is no need to convince someone to come to a side like Roma.
"With Seydou we often discussed the Giallorossi and Francesco Totti, especially after the Champions League games. He is attracted to attacking football, the kind played by Roma.
"In every transfer session I am called by many clubs, because he is a player who has always scored regularly. He also faced Manchester City four times, scoring five goals and earning a penalty.
"I don't think he will struggle to adapt to Serie A. After all, aged 18 he moved to Japan and learned the language. He also showed what he can do straight away in Russia."
His agent also said Doumbia will wear the uncoventional No. 88 shirt at Roma.