Rosenberg is located in central Fort Bend County at 29°33′9″N 95°48′18″W / 29.55250°N 95.80500°W / 29.55250; -95.80500 (29.552388, -95.804899), on the south side of the Brazos River. It is bordered to the northeast by Richmond, to the south by Pleak, and to the southwest by Beasley.
The Southwest Freeway (I-69 and US-59) runs through the south side of Rosenberg, bypassing the city center. The freeway leads northeast 32 miles (51 km) to downtown Houston, and US-59 continues southwest 92 miles (148 km) to Victoria and beyond.
According to the United States Census Bureau, Rosenberg has a total area of 22.5 square miles (58.4 km), of which 22.5 square miles (58.2 km) are land and 0.04 square miles (0.1 km), or 0.25%, is water.
At the 2000 census, there were 24,043 people, 7,933 households and 5,976 families residing in the city. The population density was 1,131.7 per square mile (436.8/km²). There were 8,438 housing units at an average density of 397.2 per square mile (153.3/km²). The racial makeup of the city was 65.69% White, 8.53% African American, 0.37% Native American, 0.38% Asian, 0.04% Pacific Islander, 22.17% from other races, and 2.81% from two or more races. Hispanic or Latino of any race were 54.96% of the population.
There were 7,933 households of which 41.3% had children under the age of 18 living with them, 53.4% were married couples living together, 15.7% had a female householder with no husband present, and 24.7% were non-families. 20.8% of all households were made up of individuals and 8.1% had someone living alone who was 65 years of age or older. The average household size was 3.00 and the average family size was 3.48.
30.9% of the population were under the age of 18, 10.8% from 18 to 24, 30.0% from 25 to 44, 18.5% from 45 to 64, and 9.8% who were 65 years of age or older. The median age was 30 years. For every 100 females, there were 98.6 males. For every 100 females age 18 and over, there were 95.2 males.
The median household income was $35,510 and the median family income was $39,965. Males had a median income of $28,723 versus $21,945 for females. The per capita income for the city was $14,814. About 13.6% of families and 16.1% of the population were below the poverty line, including 20.7% of those under age 18 and 12.9% of those age 65 or over.