Washington in a corresponding roster move designated right-hander Joan Adon for assignment.
Rosario played the bulk of games at shortstop while also seeing time at second base, third base and all three outfield positions.
Amed Rosario — who started his career with the Mets and played four years in Queens — and the Washington Nationals agreed to a one-year, $2 million contract on Wednesday.
While playing for those three teams, Rosario hit .280 with three home runs and 32 RBIs to go along with 18 doubles, three triples, 13 stolen bases and 29 runs scored.
Rosario, who is headed into his ninth major league season, is the latest addition by the Nationals after they acquired first baseman Nathaniel Lowe in a trade with the Texas Rangers and signed Josh Bell as a free agent.
