Rosenberg was born in Marin County, California. Her father is Jack Lee Rosenberg, a psychotherapist and the founder of integrative body psychotherapy. Her mother was Patricia Rosenberg, a lawyer. She was the second of four children by her father's first marriage and another by his second. Rosenberg's father was Jewish, and her mother was of Irish Catholic background.

As a child, Rosenberg enjoyed presenting plays and recruiting other neighborhood children to perform in them. She attended a "massive public high school with a crowd of people bunched in a classroom and expected to learn" in Southern California. She later moved to New York City to join a small theatre company before moving again to Bennington, Vermont to attend Bennington College. She originally aspired to work in Dance and Choreography, which she studied in college and describes as her "first love". She says she began too late, however, so she moved to Los Angeles, California to pursue a career in the film industry instead. She graduated from the University of Southern California's (USC) Peter Stark Producing Program with a Master of Fine Arts degree in film and television producing.

Rosenberg's first project was a dance film commissioned by Paramount Pictures that was ultimately never made. She then shifted to television writing. She first wrote for Class of '96 in 1993, and went on to work on shows including Dr. Quinn, Medicine Woman (1995—1996), Dark Skies (1996), The Magnificent Seven (1998), Ally McBeal (2001) and Birds of Prey (2002) before she came to join the writing staff of The O.C. in 2003. Leaving The O.C. at the conclusion of its first season, she was hired to write her second screenplay, the 2006 dance film Step Up. (Later, she was also offered the job of writing the sequel, Step Up 2 the Streets, but turned the offer down as she was busy with other projects.) Rosenberg went on to write for the television series Love Monkey (2006) and Dexter (2006—present). Her job on Dexter, which is broadcast on Showtime, was her first on a show written for cable...she stated in 2007, "Cable is the place to be ... it's just wonderful." She and the other members of the Dexter writing staff were nominated for a Writers Guild of America Award for best Dramatic Series at the February 2008 ceremony for her work on the first season of Dexter. She was nominated for the same award at the February 2009 ceremony for her work on the third season of Dexter. As an executive producer was also co-nominated for the Outstanding Drama Series award at the 60th Primetime Emmy Awards. She was nominated for the WGA award a third consecutive time at the February 2010 ceremony for her work on the fourth season of Dexter.

Summit Entertainment, the production company which had produced Step Up, offered Rosenberg the chance to adapt Stephenie Meyer's bestselling novel Twilight into a film of the same name, which she accepted. Her primary inspiration for the adaptation was Brokeback Mountain, which she described as a "great model" of forbidden love alongside Romeo and Juliet, and thought its adaptation from short story to film was "beautiful". She was given a "manifesto" written by Meyer outlining everything that had to be included or could not be changed in the adaptation. She wrote a detailed 25-page outline in August 2007, expecting to have another two months to write the actual screenplay, but had only five weeks to finish the script before the commencement of the 2007—2008 Writers Guild of America strike. After the release of Twilight, she was hired by Summit to adapt the sequels New Moon and Eclipse, the second and third books in the series, respectively, and she had already begun drafting the New Moon screenplay by November 2008.

Rosenberg was on the Writers Guild of America's Board of Directors for five years before stepping back because "you can get really, really wrapped up in it". She was very active, however, in the 2007—2008 Writers Guild of America strike, standing on the line as a strike captain. She is currently involved in the WGA Diversity Committee supporting female screenwriters, but is more active in the League of Hollywood Women Writers, which she and several other women set up while on strike, aiming to fight the "boys' club mentality" in television writing rooms.

Rosenberg's mother died when Rosenberg was a teenager, after her father had remarried to Lynn MacCuish; he later married again to fellow therapist Beverly Kitaen-Morse. She has an older sister, Andrea (born 1960), younger brother and sister Erik and K. C. (twins, born 1963), and a younger half-sister, Mariya (born 1981), by her father's second wife.

Rosenberg lives in Los Angeles with her husband Lev L. Spiro, a television director, and their dog Zuma. She joked that "At our wedding, half the attendees were shrinks, the other half, their clients," after explaining that "My sister is a dance therapist; my other sister is in graduate school to become a therapist. My husband's parents are both shrinks. His uncle, two aunts and sister are shrinks."

Films

Television