The 20-year old attacking midfielder, who can also be deployed as a striker, has had a transfer request accepted with his shift to Germany set to be complete in the next few days according to reports.
Dusseldorf, where fellow Australian youngster Robbie Kruse played last season, will compete in the 2.Bundesliga next term after they were relegated from the top flight.
"We never want to stand in the way of a player pursuing their dreams overseas," Roar managing director Sean Dobson said today.
"As a club, we've got a great tradition of footballers forging successful careers overseas.
"We've enjoyed having Ben here and we hope he goes on to do great things in Germany."