She began her writing career at the San Francisco Zoological Society, producing press releases on such topics as elephant wart surgery. In 1986, she sold a humor piece about the IRS to the San Francisco Chronicle. That led to a spate of humorous first-person essays for such publications as Sports Illustrated, Vogue, The New York Times Magazine, Discover, Outside, Reader's Digest (for whom she wrote a monthly humor column) and GQ. She appeared on The Colbert Report, a satirical news program, in November 2005.

Roach's work has a serious edge, as well. Her book, The Curious Lives of Human Cadavers, was selected for Washington State University's Common Reading Program in 2008-09.

Roach appeared on The Daily Show on August 2, 2010 to discuss her newest book Packing for Mars.