Rosanna "Rosie" Dagmar Pen Hansen (born April 21, 1975) is an American actress and writer, the star and writer of the Emmy Award-winner sitcom, Change. Except of that, she also wrote the screenplay of the fantasy series The Keys to the Kingdom and also starred and wrote sketches for five years in the NBC sketch show, Wednesday Nights.

Pen Hansen was born to Swedish immigrants in Fort Wayne, Indiana. Her mother, Gertrude Pen, is a poet and her father Anderas Pen is an architect. Pen Hansen was born with the name Rosanna Dagamr Pen. In 1992, she added her mother's maiden name, Hansen, to her family name. So far, Pen Hansen was never credited in her full name, only by her stage name, Rosie Pen Hansen. Pen Hansen has two sibling: Jensen, a judo coach, and Ulla Thompson, an actress.

Pen Hansen was graduated in the North Side High School in Fort Wayne and went to do community theatre in New York City. She later appeared as a guest in Wednesday Nights, playing drug addict Loolie Loo. The audience loved and role and the producers decided to give her a constant role in thw show, also starring as the flower girl Mimi and the lesbian basketball player Amanda Ball. The role of Loolie Loo in the show even bring her a short-lived sitcom on NBC, called Loolie Loo and the Elephants. During her work on the sketch show, she made guest appeareances in ER, Futurama and even Days of Our Lives.

In 1999, together with Conan Cannon, she started working on a sitcom. She sent the pilot to NBC and they accepted the show, giving it the name Change. The show was about an engaged couple living in the same apartment with the guy's best friend and the woman's broke friend from high school. The show premiered on NBC on May 1, 2000 with Pen Hansen starring as Liza Herman and also starred by Conan Cannon, Gail Wokoraend and Googi Smith. Change won the Emmy Award for the best comedy in 2001 and 2003.