Miss Beard, 25, had been travelling through the South Island on her way to meet up with her fiance Reg Phillips, with whom she was due to go tramping, when she disappeared.
It is believed she was strangled in a sexually motivated attack on New Year's Eve. Her body was found under the Haast River Bridge 19 days later.
Roberts said she had never expected to make a film on such a subject.
"I basically started doing private investigation work about five years ago, and I never really thought I would be getting into investigating an unsolved murder.
"I woke up one day and her name was suddenly stamped on my brain, I didn't even know who she was... I thought who is this person, so I started researching her.
"From then on I just kept bumping into witnesses. The first witness came to me, I didn't have to go looking. I put something in the paper about some information, and it's been snowballing from there."
The film had been almost entirely self-funded and paid for by West Coasters, Roberts said.
The story was still relevant because of the huge impact the aftermath of Miss Beard's murder had on New Zealand.
"New Zealand hadn't seen anything like it, there were hundreds and hundreds of people, army, policemen, thousands and thousands of Vauxhall Velox cars were checked, it was just astronomical."
- The Westport News
