Rollinsville is a census-designated place and a U.S. Post Office located in Gilpin County, Colorado, United States. The population as of the 2010 Census was 181. It is located in the mountains southwest of the city of Boulder, on the flank of a hill above South Boulder Creek along State Highway 119 between Nederland and Black Hawk. It consists of a small cluster of residences and several businesses at the terminus of the road leading westward up to Rollins Pass at the summit of the Front Range.