Part of the Red Lake Indian Reservation is in Roseau County.

Roseau County was once the home of many Ojibwe, Sioux, and Mandan tribes.

Archeologists have found artifacts within the county belonging to these tribes that date back 7,200 years.

On December 31, 1894,[5] Governor Knute Nelson proclaimed the eastern portion of Kittson a new county, to be named Roseau.

The county terrain consists of low rolling hills, devoted to agriculture, and dotted with lakes and drainages.

In presidential elections, Roseau is Minnesota's most reliably Republican-voting county.

John McCain's and George W. Bush's best performances in Minnesota were in Roseau County.

Roseau County is less reliably Republican in senatorial and gubernatorial elections.

In the 1998 gubernatorial election, Norm Coleman's best performance in Minnesota was in Roseau County, where he won with almost 50% of the vote.