Roseland was incorporated as a borough by an Act of the New Jersey Legislature on March 10, 1908, from portions of Livingston Township.
New Jersey Monthly magazine ranked Roseland as its 14th best place to live in its 2008 rankings of the "Best Places To Live" in New Jersey.
As of the census of 2000, there were 5,298 people, 2,142 households, and 1,525 families residing in the borough. The population density was 1,463.6 people per square mile (565.1/km²). There were 2,187 housing units at an average density of 604.2/sq mi (233.3/km²). The racial makeup of the borough was 93.43% White, 0.72% African American, 0.04% Native American, 4.72% Asian, 0.43% from other races, and 0.66% from two or more races. Hispanic or Latino of any race were 2.28% of the population.
As of the 2000 census, 32.0% of Roseland residents were of Italian ancestry, the 27th-highest percentage of any municipality in the United States, and 10th-highest in New Jersey, among all places with more than 1,000 residents identifying their ancestry.
There were 2,142 households out of which 26.2% had children under the age of 18 living with them, 60.8% were married couples living together, 7.9% had a female householder with no husband present, and 28.8% were non-families. 25.7% of all households were made up of individuals and 13.4% had someone living alone who was 65 years of age or older. The average household size was 2.47 and the average family size was 2.99.
In the borough the population was spread out with 20.6% under the age of 18, 4.2% from 18 to 24, 26.3% from 25 to 44, 29.2% from 45 to 64, and 19.7% who were 65 years of age or older. The median age was 44 years. For every 100 females there were 85.9 males. For every 100 females age 18 and over, there were 82.6 males.
The median income for a household in the borough was $82,499, and the median income for a family was $93,957. Males had a median income of $61,049 versus $41,688 for females. The per capita income for the borough was $41,415. None of the families and 1.7% of the population were living below the poverty line, including no under eighteens and 2.7% of those over 64.