The Blue Jays made the move Thursday and also recalled right-hander Brad Lincoln from Triple-A Buffalo.
Johnson was scratched from a start Friday, and his move to the DL was retroactive to April 29. He is 0-1 with a 6.86 ERA in four starts since being acquired in an offseason trade with Miami.
Romero will start Friday night at home against Seattle. He was an All-Star in 2011, but struggled in spring training this year and began the season in the minors to work on his mechanics.
Romero made one start for Class A Dunedin, allowing one run in seven innings.
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