Rocklin is part of the Sacramento–Arden-Arcade–Roseville Metropolitan Statistical Area.
As of the 2008, there were 53,843 people, 13,258 households, and 10,009 families residing in the city. The population density was 2,246.2 people per square mile (867.5/km²). There were 14,421 housing units at an average density of 891.6/sq mi (344.3/km²). The racial makeup of the city was 88.32% White, 0.91% African American, 0.80% Native American, 4.16% Asian, 0.19% Pacific Islander, 1.93% from other races, and 3.69% from two or more races. Hispanic or Latino of any race were 7.91% of the population. 16.8% were of German, 11.8% English, 10.6% Irish, 8.1% Italian and 6.5% American ancestry accoding to Census 2000.
There were 13,258 households out of which 42.6% had children under the age of 18 living with them, 62.3% were married couples living together, 9.4% had a female householder with no husband present, and 24.5% were non-families. 18.7% of all households were made up of individuals and 6.3% had someone living alone who was 65 years of age or older. The average household size was 2.74 and the average family size was 3.15.
In the city the population was spread out with 30.0% under the age of 18, 7.0% from 18 to 24, 33.7% from 25 to 44, 20.8% from 45 to 64, and 8.6% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 95.6 males. For every 100 females age 18 and over, there were 92.6 males.
The median income for a household in the city was $84,508, according to the City of Rocklin website. Males had a median income of $54,426 versus $35,920 for females. The per capita income for the city was $26,910. About 3.1% of families and 4.5% of the population were below the poverty line, including 4.3% of those under age 18 and 3.5% of those age 65 or over.
Rocklin is served by Interstate 80 and State Route 65. Work on a new interchange at Sierra College Boulevard and I-80 is near completion. There is an Amtrak station in Rocklin that is served by the Capitol Corridor and the California Zephyr routes.