Rosenberg is a city in the U.S. state of Texas, within the Houston–The Woodlands–Sugar Land metropolitan area and Fort Bend County. The population was 30,618 at the 2010 census, up from 24,043 at the 2000 census. As of 2015, the population had risen to an estimated 35,510. The community holds the Fort Bend County fair in October. Rosenberg sits adjacent to the city of Richmond, the Fort Bend County seat.