Romero had been one of the best lefty relievers in the game as recently as 2005, but struggled last year for the Angels and could never get into a rhythm with the Red Sox.
The Red Sox now have 10 days to release, trade or re-assign Romero, with the middle option seeming to be the likeliest.
"I know that [general manager] Theo [Epstein] talked to his agent," said Francona. "They're trying to make a trade to a place where J.C. can help. That was the move we had to make. That's not a fun way to celebrate a win."
Romero's final outing in a Boston uniform came on Monday night, when he managed to wiggle out of a bases-loaded, nobody-out jam in the bottom of the ninth inning at Oakland.
He struggled with his control, issuing 15 walks in 20 innings. Romero appeared in 23 games for Boston, going 1-0 with a 3.15 ERA.
However, fellow lefty Hideki Okajima has emerged into a big force out of the bullpen for Boston, and southpaw Javier Lopez has also been solid as a specialist, making Romero expendable.
"The emergence of Oki has been unbelievable," Francona said. "He's been a go-to guy. Because of that, then you couple him with Javy, sometimes you have to make very difficult decisions that aren't a lot of fun and that's' what we did."
The Red Sox signed Romero to a one-year, $1.67 million contract back in December.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.