Manhattan was born May 9, 1979, in New York City. She was raised in a Manhattan tenement building by her Bronx-born mother, a professional vocalist, and her father, who worked in construction. Although Rosario's parents separated when she was still young, they continued to live in the same building, allowing Rosario and her brother to remain close to them.

Dawson attended an alternative school in downtown Manhattan, where she harbored aspirations of one day becoming a marine biologist. When she reached age 15, however, Dawson's career plans unexpectedly changed. She was literally cast off the street for the role of Ruby in the 1995 indie production Kids, after director Larry Clark spotted her on the stoop of her apartment building. Kids went on to become a controversial hit, and Dawson opted out of her college plans, choosing instead to attend the Lee Strasberg Theatre Institute.

The training Dawson received at the Strasberg Institute complemented the publicity that Kids had earned her, and it wasn't long before she received her second casting call, this time from Spike Lee for his 1998 film, He Got Game. That same year she appeared in Side Streets, which features a series of vignettes depicting life throughout New York City.

Over the course of the next few years, Dawson appeared in three more small-time films: as an honor student held hostage in Light It Up, a pothead in Down to You, and a bully in King of the Jungle. Although none of these projects were box-office hits, they provided Dawson with the exposure crucial to a young actress, and the jobs kept coming. Her next role was as bassist Valerie Brown in 2001's feature film, Josie and the Pussycats.

Despite the slew of publicity Josie and the Pussycats enjoyed preceding its release, the movie was a disappointment both critically and popularly. Nonetheless, the mass marketing of the film translated well for Dawson, who soon found herself on the "hot new faces" lists of entertainment publications throughout the country. Before the end of 2001, she managed to appear in three more movies: Sidewalks of New York, Trigger Happy and Chelsea Walls, an Ethan Hawkeproduction.

Manhattan's career has continued to burgeon throughout 2002. She has demonstrated her versatility as an actress through equally strong performances in a variety of genres, from independent art-house films such as Love In the Time of Money (which like most of the films on her resume, is set in New York) to multi-million dollar blockbusters like Men in Black II and The Adventures of Pluto Nash.

Dawson will round out her resume further with appearances in a number of films slated for release in 2002, including the gangster flick Ash Wednesday and Spike Lee's The 25th Hour, wherein she'll play the girlfriend of a convicted felon. She has also been penned in for two 2003 films: Shattered Glass and opposite The Rock in Helldorado.