Goal understands Emerson has agreed a four-and-a-half year contract at Stamford Bridge, with around £8m of performance related add-ons set to be included within the deal.
As previously reported, all parties had been in agreement on a move but the deal has been held up by the Blues' interest in Emerson's team-mate Edin Dzeko.
Chelsea remain open to bringing in Dzeko but are sounding out alternatives as the Serie A outfti have become harder to negotiate with amid fan pressure to keep their star striker..
Emerson is set to arrive after Chelsea's failed attempts to sign Juventus wing-back Alex Sandro, withAntonio Conte having targeted signing a full-back to challenge Marcos Alonso during the winter window.
The arrival of Emerson comes after fellow full-back Kenedy left for Newcastle on loan, while Chelsea are also sanctioning a temporary move for Baba Rahman to return to Schalke 04.
The Roma defender has only recently recovered from an anterior cruciate ligament injury, but is expected to pass his medical after recently returning to the pitch to make two appearances this season.
The former Palermo man impressed at Roma last season but the Giallorossi need to sell in order to continue their compliance with Financial Fair Play.
His arrival will mark Conte's second signing of the January window after Ross Barkley completed his £15m move from Everton earlier this month.