Gregory Roosa joined the Los Angeles Philharmonic as Second Horn in September. Prior to that, he had held the Fourth Horn position in the St. Louis Symphony Orchestra since 2003. He performed as soloist with the SLSO in 2007. His previous positions include Fourth Horn with the Kennedy Center Opera and Ballet Orchestra, and Fourth Horn with the Colorado Symphony in Denver.

A native of Troy, Michigan, Roosa earned a Bachelor of Music degree from the University of Illinois and studied with Ralph Froelich at the University of South Florida. In 1992, he moved to Chicago to study with Dale Clevenger, Principal Horn with the Chicago Symphony, and was a member of the Civic Orchestra of Chicago for three seasons. Active as a freelance musician in the Chicago area for eight years, Roosa played the Broadway shows Ragtime, Phantom of the Opera, and Miss Saigon. He also played with the Chicago Symphony Orchestra, including a European tour and two recordings. Roosa has appeared as soloist and clinician at numerous universities and horn workshops around the world.

Roosa has performed with the Melbourne Symphony Orchestra and Queensland Orchestra in Australia, as well as with the Florida Orchestra and Detroit Symphony in the United States. He has been a member of the Colorado Music Festival Orchestra since 1999, where he met his wife, Amy Jo Rhine, who is also a horn player. Together they have two young boys, Norton and Sutton.

Roosa is an enthusiastic cyclist who has ridden in several Century Rides in Colorado and has competed in a professional race to the top of 14,000-foot Mt. Evans, near Evergreen, Colorado, in 2009. Roosa and his family enjoy hiking and camping during their Colorado summers.