Roosevelt County is a county in the U.S. state of Montana. As of the 2020 census, the population was 10,794. Its county seat is Wolf Point. Roosevelt County was created by the Montana Legislature in 1919 from a portion of Sheridan County. The name honors former president Theodore Roosevelt, who had died earlier that year.

The Fort Peck Indian Reservation is located near Fort Peck, Montana, in the northeast part of the state. It is the home of several federally recognized bands of Assiniboine, Lakota, and Dakota peoples of Native Americans.