Roush made his Major League debut on August 20, 1913 for the Chicago White Sox. He played seasons for the Indianapolis Hoosiers, Neward Pepper and New York Giants before finding a home as a member of the Cincinnati Reds in 1916. With the Reds from 1917 to 1926, Roush never batted below .321 and was an instrumental part of the team's World Series championship in 1919. He won the batting title in 1917 and 1919.
Roush played for the New York Giants again from 1927 until 1929 and rejoined the Cincinnati Reds for a single season in 1931 before retiring. He sat out the 1930 season over a salary dispute.
Roush finished his career with a .323 average, 268 stolen bases and 182 triples. He never struck out more than 25 times in a season and had 30 inside-the-park home runs.
Roush was elected into the Baseball Hall of Fame in 1962.