Rosenberg is a city in the U.S. state of Texas, within Houston–The Woodlands–Sugar Land metropolitan area and Fort Bend County. The population was 31,676 at the 2010 census. The community holds the Fort Bend County fair in October. Rosenberg sits adjacent to the city of Richmond, TX. Rosenberg is named after Henry Rosenberg who migrated from Switzerland to the United States in 1843. He was the first president of the Gulf, Colorado & Santa Fe Railroad.According to the United States Census Bureau, the city has a total area of 21.3 square miles (55 km2), of which 21.2 square miles (55 km2) is land and 0.05% is water.