Update (5:36 PM EST): That minor leaguer is pitcher Jeffrey Rosa, per MASN’s Mark Zuckerberg. Rosa, 21, pitched 40 1/3 innings across 11 starts for the Nationals’ rookie league team last season.
Romero, 26, has a career 5.27 ERA and an 81/45 K/BB ratio across 80 1/3 innings in the majors. The lefty was out of options and the Rays were likely to designate him for assignment at some point before the start of the season, so the club took their opportunity to get value and open up a roster spot.
Romero won’t be eligible for arbitration until 2019, so the Nationals will have a couple years to help him figure out how to control his arsenal, which includes a mid-90’s fastball as well as a cutter and a curve.