Ryan, 1-0 with an 11.12 ERA in six games, was placed on the 15-day disabled list April 23 with muscle tightness in his back and shoulder, one day after blowing his second save in four chances.
Ryan is in the fourth year of a five-year, $47 million contract. He missed most of the 2007 season following elbow-ligament replacement surgery and recorded 32 saves last year.
Manager Cito Gaston said Ryan likely will pitch twice at Class A Dunedin before moving up to Double-A New Hampshire.
Left-hander Scott Downs has gone 3-for-3 in save opportunities since Ryan went down.
Romero, a rookie, went 2-0 with a 1.71 ERA in three starts before he was placed on the 15-day DL on April 20 with a strained muscle in his right side. General manager J.P. Ricciardi said Romero will start for Dunedin on Friday and again next Wednesday before being re-evaluated.
Right-hander Casey Janssen (shoulder), who has not pitched for Toronto this season, will make two more starts at Dunedin before being re-evaluated, Ricciardi said, meaning both he and Romero could join the Blue Jays at the same time.
Right-hander Jesse Litsch, out since April 14 with a strained forearm, is throwing in Florida and should be ready to pitch in games in about a week.
Ricciardi had mixed news on two right-handers who had surgery last season. Shaun Marcum (elbow) will throw bullpens for the rest of May and could pitch in minor league games by June. Dustin McGowan (shoulder) is playing catch from 60 feet and may not return this season.