It was established February 11, 1901, and has Montana vehicle license plate prefix 29.

Part of Custer National Forest is located in the county.

[citation needed] As of the 2010 census, there were 9,233 people, 3,395 households, and 2,318 families residing in the county.

In terms of ancestry, 25.0% were American, 19.0% were German, 6.9% were English, and 6.6% were Irish.

Rosebud County voters have voted for the Republican Party candidate in all national elections since 2000 (except 2008).