Bill Roach murder: $1 million reward for information about suspected murder of William 'Bill' Roach in Armidale in 1994

William 'Bill' Roach, just 25 years old, was spotted walking along an Armidale street in the NSW New England region on New Year's Eve in 1993, before vanishing without a trace.

Police are probing what could possibly have happened to the 25-year-old, and announced on Tuesday they had upped the reward for information ten fold - from $100,000 to $1 million.

A special squad, dubbed Strike Force Annan, was launched in 2004 by New England detectives to investigate the mysterious disappearance and suspected murder of the Armidale man.

Investigations during the decades have failed to solve the mystery of the Armidale man, including police executing a crime scene warrant at a home on the outskirts of Armidale in 2016.

His body has never been found, but a coronial inquest found it was likely Mr Roach had died.

The Leader exclusively interviewed a man originally questioned about the case, Martin Rummery, in 2016, who said he wished he could help give the family closure but couldn't shed any light on what happened.

NSW police minister David Elliot, New England Detective Superintendent Steve Laksa, flanked by Mr Roach's sister Kim Roach, gathered in Sydney on Tuesday morning to announce the reward for information had been increased to $1 million.