The Nigeria under-23 global is set to arrive in Glasgow for a season-long loan, and could even feature in some capacity on Thursday evening, should the Gers complete the paperwork for the move by Wednesday.
The 21-year-old has had spells at Bologna, Torino and NAC Breda in recent years and will leave the Stadio Olimpico on a temporary basis once again to join the Light Blues' attack this term.
The move, which is subject to worldwide clearance, will see the 22-year-old become Steven Gerrard's eighth signing of the summer. Coulibaly told Rangers TV.
"At the moment, he (Sadiq Umar) is still a Roma player but it has been well documented that I am a fan, but it's just a case of watch this space", Gerrard told reporters on Saturday evening.
Protests, pro-rallies planned across United Kingdom ahead of Trump's visit
The biggest protest will take place in central London on Friday when thousands are expected to take to the streets to join the "Stop Trump" march .
"Rangers are a good team and I knew the name before Gerrard came in".
He must now turn his attention to Thursday's Europa League qualifying match against Macedonian team FK Shkupi.
Capped nine times by Mali, Coulibaly will be part of a cast of players expected to star in Gerrard's first top-flight football managerial test.
They will become the eighth and ninth signings of Gerrard's tenure, following Scott Arfield, Allan McGregor, Jamie Murphy, Nikola Katic, Connor Goldson, Ovie Ejaria and Jon Flanagan in moving to Ibrox. "When they asked me if I want to join this team or not, I said yes but I thought it might not really be Gerrard!"