The film was re-released theatrically in North America in April 2015. A list of showtimes in various US cities is here: http://drafthousefilms.com/film/roar#watch
Blu-ray and DVD versions are out on November 3, 2015.
http://www.amazon.com/Roar-Blu-ray-Noel-Marshall/dp/B00VYL4JT2/