[3] The county was named either for S. G. Roberts of Fargo, North Dakota, or for Solomon Robar, an early local French fur trader.

[4] Roberts County is at South Dakota's northeastern corner.

The Cottonwood Slough flows southward, draining the upper portion of the county into the River.

[5] The terrain slopes to the east; its highest point is on its upper western boundary line, at 2,047 ft (624 m) ASL.

[7] The Traverse Gap is in eastern Roberts County along the Minnesota border.

As of the 2020 census, there were 10,280 people, 3,844 households, and 2,568 families residing in the county.