Roberts will produce and star in the film about wildlife conservationist Joan Root, who was killed in her home in Kenya this year, The Daily Variety reported Sunday.
An article from the magazine Vanity Fair, titled "A Flowering Evil," inspired Roberts to do the movie. The film will show Root making documentaries around the globe with her husband, then getting a divorce and moving to Kenya where she worked on saving Lake Naivasha from the ecologically damaging flower farm industry.
Roberts and WT last worked together on the box office hit "Notting Hill."
WT has six other films set to release in 2007 as well, four in the United States and two in Britain.