Rollag is a municipality in Buskerud county, Norway. It is part of the traditional region of Numedal. The administrative centre of the municipality is the village of Rollag, although the most populated area in the municipality is Veggli. Rollag is bordered in the north by Nore og Uvdal, in the east by Sigdal, in the south by Flesberg, and in the west by Tinn in Telemark.

Buskerud is a county and a current electoral district in Norway, bordering Akershus, Oslo, Innlandet, Vestland, Telemark and Vestfold. The region extends from the Oslofjord and Drammensfjorden in the southeast to Hardangervidda mountain range in the northwest. The county administration was in modern times located in Drammen. Buskerud was merged with Akershus and Østfold into the newly created Viken County on 1 January 2020. On 23 February 2022, the Viken County Council voted in a 49 against 38 decision to submit an application to the Norwegian government for a county demerger. Due to this, Buskerud was re-established in 2024.