At the age of 19, Rooney won a gold medal at the 2017 IIHF Women's World Championship as a backup goaltender. She recorded a shutout in her only game of the tournament, which came against Russia in the preliminary round. In 2018, she was again selected to play for the U.S. women's national ice hockey team at the Winter Olympics in Pyeongchang. Rooney started all but one of the games in the competition, losing only one game to Canada during the round robin. She helped lead Team USA to the gold medal by winning the shootout in the final against Canada by a score of 3–2, stopping Meghan Agosta in the sixth and last round to end the game. It was the United States' first gold medal at the Olympics since 1998, ending the Canadians' streak of four consecutive Olympic championships.