The name honors former president Theodore Roosevelt, who had died earlier that year.

[4] Three-fourths of the county's land area lies within the Fort Peck Indian Reservation.

[citation needed] As of the 2010 census, there were 10,425 people, 3,553 households, and 2,548 families residing in the county.

Roosevelt County is competitive in presidential elections, due to its high Native American population.

In 2024, the county trended more strongly in the conservative direction when it gave Trump a 53% majority.