The deal, subject to global clearance, makes the Mali worldwide Steven Gerrard's eighth signing for the Gers, ahead of his first managerial stint.
UMAR Sadiq admits he planned to stay at Roma this season before the lure of Steven Gerrard steered the striker all the way to Glasgow.
Sadiq, 21, has struggled to pin down a regular shirt since linking up with AS Roma from Serie B side Spezia in 2015.
"The 22-year-old makes an exciting eighth addition to Steven Gerrard's squad as the manager strengthens his midfield options even further". Coulibaly told Rangers TV.
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"He told me about the players and said everybody would be at my side if I came here to help me and he would also help me to go forward in my career".
"I'm very happy to be here", Coulibaly, capped nine times for Mali, said.
"He asked me if I wanted to join his team, and I said yes, although I was anxious it wasn't actually Gerrard (on the phone)!" the Malian said.
Mali worldwide Coulibaly, who has been capped 10 times, admits the lure of playing for Gerrard was too good to turn down.
But with midfield signings being made at Angers across this summer, Coulibaly was going to find first team chances hard to come by, but at Rangers the Mali International will likely be heralded as one to watch throughout the campaign.