In his second stint this season with the Orioles organization, Romero will be officially activated and added to Baltimore's 25-man roster prior to Tuesday's game.
It also might not be the only roster move the club makes prior to the Red Sox series. The Orioles are dealing with a potential disabled-list situation and are prepared to activate right-handed pitcher Steve Johnson, if needed, prior to Tuesday's game.
On Wednesday, Johnson was optioned to Triple-A Norfolk a day after his first career Major League start, and he would not be eligible to return to the club until Sunday unless there's a DL situation. He was originally scheduled to start for Norfolk on Tuesday.
In the deal, Cleveland acquired Rojas, 28, and in two stops at Double-A Bowie and Triple-A Norfolk, he was hitting .226 with 10 runs and nine RBIs.
Romero will take the roster spot of right-handed pitcher Miguel Socolovich, who was optioned after Sunday's game, and gives the Orioles another lefty in the bullpen along with Troy Patton.
Romero, who could have opted out of his deal with Cleveland on Wednesday, spent nearly two months with the Orioles after he was released by the Cardinals in May. But he never made it to the big league club until now, despite pitching well with Norfolk. The 36-year-old has pitched to a 2.74 ERA in 23 Minor League innings this year after posting a 10.13 ERA in 11 games (eight innings) for St. Louis.
The Orioles are also still in need of a starter for Saturday's game and are currently employing a four-man rotation.
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.