Roberts County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 10,280. Its county seat is Sisseton. The county was named either for S. G. Roberts of Fargo, North Dakota, or for Solomon Robar, an early local French fur trader. It was created on March 8, 1883, and fully organized by August 6 of that year. Its boundary was altered once, in 1885.

Sisseton is a city in Roberts County, South Dakota, United States. The population was 2,479 at the 2020 census. It is the county seat of Roberts County. Sisseton is the home to a number of tourist attractions, including the Nicollet Tower, and is near the "Song to the Great Spirit" building on the Sisseton Wahpeton College campus. The city is named for the Sisseton division of the Native American Sioux. It also serves as an important part of the Lake Traverse Indian Reservation.