Former 'Sex Rehab' Star Duncan Roy -- I Didn't EXTORT Anyone!!!

The former "Sex Rehab with Dr. Drew" star who's accused of attempting to extort a mystery victim in a threatening letter appeared in an L.A. courtroom today and pled not guilty to the crime ... TMZ has learned.

TMZ broke the story ... Duncan Roy -- who directed the 2002 indy hit "AKA" -- was arrested last week for felony attempted extortion.

It's still unclear who Roy allegedly tried to extort -- and what he allegedly demanded.

Today, Roy's lawyer argued that as a movie maker with two projects in the works, Roy should be granted bail so that his employees can keep working. The judge obliged -- and set Roy's bail at $35,000 ... though Roy has yet to be released.