Romero was placed on the 7-day injured list Wednesday for Triple-A Columbus with right elbow soreness.
Romero signed a minor-league contract with the Guardians on Monday.
Romero (biceps) was placed on outright waivers on Tuesday by the Twins, Brandon Warne of Access Twins reports.
Romero (biceps) was transferred to the 60-day injured list Wednesday.
Romero was designated for assignment by the Nationals on Thursday, Mark Zuckerman of MASNSports.com reports.
Romero's contract will be selected from Triple-A Rochester on Thursday, Jesse Dougherty of The Washington Post reports.