He first produced the Canadian feature A Great Big Thing (1968) and later co-produced Ken Russell's film version of Women in Love (1969), which won Academy Awards for Glenda Jackson and Billy Williams (cinematographer) Rosen was originally the producer of Watership Down but took over as director after John Hubley, the original director, left after disagreements with Rosen.
He was the originating producer of Michael Weller's Moonchildren, first presented at London's Royal Court Theater before transferring to the US.
In his ruling, Judge Richard Hacon ordered Rosen to pay over $100,000 in damages for copyright infringement, unauthorised license deals, and denying royalty payments to the Adams estate.
He was also directed to provide a record of all license agreements involving Watership Down and pay court costs and the Adams estate's legal fees totalling £28,000.
[2] Subsequent failure to comply with the terms of the UK judgement left Rosen in contempt of court and facing enforcement proceedings in Connecticut.