Won a silver medal with Team USA at the Tokyo 2020 Olympic Games, making three appearancesf or the stars and stripes. He came on in the ninth inning against Korea in the Group B finale and picked up the save, striking out one batter and surrendering a run. His strikeout in the ninth inning against Korea tied the U.S. Olympic team record for strikeouts in a game with 14. Robertson pitched an inning of scoreless relief against Japan in the quarterfinals, striking out two, and picked up the save against the Dominican Republic while striking out one batter in the 3-1 victory that secured Team USA's spot in the semifinals.

2021 Qualifier: Robertson notched two saves to lead Team USA's bullpen at the WBSC Baseball Americas Qualifier. He earned the save in an 8-6 U.S. win over the Dominican Republic that clinched a spot in the AOQ Super Round, striking out a pair in one inning of work. The right-hander also locked up the 4-2 title-clinching win over Venezuela, striking out two batters in a hitless ninth inning.

On Team USA’s first-ever World Baseball Classic championship. In four appearances during the tournament, Robertson pitched 3.2 innings, allowed just one run, and collected two strikeouts. He was on the mound to finish the championship game, recording the final three outs to secure the 8-0 shutout win against Puerto Rico and the gold medal.