Dark questions follow missing NSW man

William "Bill" Roach was last seen in Armidale in NSW on New Year's Eve 1993.

A reward for information on the disappearance of a man in northern NSW almost 30 years ago amid rumours of witchery and the drug trade has been increased to $1 million.

Former university student William "Bill" Roach was 25 when last seen in Armidale on New Year's Eve 1993.

His body has never been found despite information he was killed on a remote farm and a 2016 search of a 1700-acre property north of the Northern Tablelands city.

The reward for information surrounding his suspected death was increased by the NSW government on Tuesday to $1 million.

The move coincides with the release of a police podcast series investigating Mr Roach's suspected murder, claims he was cursed by witches and was a player in the drug trade.

A 2010 coronial inquest concluded he had likely died but the cause of his death was undetermined.

Police Minister David Elliott says Mr Roach was a "knockabout bloke" and it could be that investigators have already spoken to his killer.

"It could be any moment now that detectives knock on your door - it is much better for you to be part of the solution," he told reporters.

Detective Superintendent Steve Laksa said Mr Roach was a "gentle soul" who likely fell into harm's way and got involved in the drug scene.

He said police were keeping an open mind but couldn't say whether lines of inquiry involving witchery and drugs were linked.

"We believe that a drugs syndicate operating at Armidale in 1993, or persons involved in the drugs syndicate may have knowledge in relation to the circumstances of Bill's death," Supt Laksa told reporters.

"There may have been people that were involved in the drug syndicate that were also involved in witchery."

Mr Roach's sister Kim believes he was met with foul play perpetrated by someone he knew.

She said her brother was jovial, handsome and smart and "girls loved him" but he had fallen in with a group she considered dishonest.

Their mother Yvonne died last year without learning of her son's fate.

"My brother Bill ... missing for 27 years, missed for 27 years, still loved immensely, the loss, the unanswered questions, the not knowing, the no closure," she said.

"We still live with the hope that someone will come forward with information, big or small. We live with the hope of closure, the hope to be able to grieve and to lay my brother Bill to rest."

Det Supt Laksa said detectives over the past 12 months had travelled as far as Tasmania to speak to people of interest.

There was also scientific evidence that was going to be re-examined in terms of the DNA, he added.

Australian Associated Press