Routh played the Man of Steel in Bryan Singer's 2006 film, "Superman Returns." Also appearing in that movie was Kate Bosworth as Lois Lane and Kevin Spacey as Lex Luther. The film, Routh's only outing as the DC legend, received at best mixed reviews.
As for this new role, Routh's Ray Palmer, aka The Atom, "Will play an unexpected role in the lives of Oliver and (rumored love interest) Felicity as the new owner of Queen Consolidated. Palmer’s plans for Queen Consolidated’s Applied Sciences Division will be shrouded in mystery."
Comic aficionados will already be aware that Ray Palmer is not the first Atom, but rather the second. The first Atom was Al Pratt. Pratt originally appeared in 1940, with Palmer not coming on until 1961. The Atom's powers include the ability to alter the size of his body.
"Arrow" is set to start its news season on October 8th and stars Stephen Amell as Oliver Queen/Arrow.