Roselyn is the youngest of four siblings - having three older brothers. She received her primary education in San Juan. At a young age, she showed an interest in both dancing and acting and would put on shows for her family. Roselyn enrolled in the University of Puerto Rico, where like her father and brothers she was to study marketing. However, this was not her calling and after three years she left the course.

In 1991, at the age of 18, Roselyn moved to New York City, where she took classes in dancing, acting and singing. She returned to Puerto Rico and in 1992, she made her movie debut, having landed a small part as an island girl in the movie Captain Ron, which was partly filmed on the island, starring Martin Short and Kurt Russell.

In 1993, Roselyn won the Miss Puerto Rico Petite contest and in 1994 she won the international title of Miss America Petite. In Puerto Rico, she gained public attention as a dancer and co-host of the island's #1 variety show, at that time, "Que Vacilon".

Roselyn returned to New York and landed her first English speaking role in the CBS soap opera, As The World Turns. She played the role of "Pilar Domingo" from 1996 until 1997.

In 2001, Roselyn was cast as "Isabella Molina", a secret customs agent who was Jackie Chan's love interest in the movie Rush Hour 2. In 2003, she played the role of "Lorena" in the movie Chasing Papi starring alongside Jaci Velasquez and Sofia Vergara.

Roselyn Sanchez has already acted in 20 movies, including the role of Maria in Edison as well as the role of Karen Lopez in Underclassman. She is also cast in the movies Venus & Vegas and Cayo which are in the post-prodution stages. She is in the process of composing a musical about a singer/dancer/actress who leaves Puerto Rico to hit the big time in New York, in this she is going to play the principal part. In 2005, her first musical recording "Borinqueña" will be out in the market. She is preparing for her role in The Perfect Sleep, a neo-noir drama, where she is co-staring with Patrick Bauchau, Tony Amendola, Isaac Singleton, and Peter Lucas. She has also joined the cast of Without a Trace.

Sánchez was married to actor Gary Stretch from 1999 to 2001. In December 2005, she announced that she had ended her longtime relationship with salsa singer, Víctor Manuelle. The separation was amicable.