In a press conference yesterday, Detective Inspector Gary Pettiford said the arrests had been the result of "many months of very professional, painstaking work" and officers would now allege Mr Saunders' death was "not an accident and that they did conspire together".
Police allege the three had plotted and then executed a gruesome plot to kill butcher Bruce Saunders in November last year.
Officers were told Saunders, 54, had accidentally fallen into the chipper while clearing a friend's property in Goomboorian, near Gympie, on the night of November 12, 2017.
On Facebook, the three accused are pictured together in a number of photographs.
In April last year, Mr Roser posted a photo of himself with Ms Graham.
Mr Roser's Facebook bio reads: "Trying to deal with life the best way I can and cull all the people that just use me".
A photo on Ms Graham's Facebook features the three accused out for dinner earlier this year, raising their drinks and smiling for the camera.
According to the Courier-Mail, Ms Graham was still living in the house of her former partner Mr Saunders when he died.
And on Tuesday, when police also arrested Ms Graham in the border town of Coolangatta, the 57-year-old was driving a car owned by Mr Saunders.
Ms Graham was listed in Mr Saunders' obituary as a "dear friend".
Police are still unable to say whether Mr Saunders was dead before he was fed into the woodchipper or died after.
All three accused appeared in Maroochydore Magistrates Court yesterday and have been in custody since. In a brief hearing, lawyers for the two men said they plan to fight the charges.
In February, Queensland Police announced Mr Saunders' horrific death — originally thought to be an accident — was actually suspicious.
Police launched a homicide investigation on February 9 after raiding the Goomboorian property, north of Gympie, the weekend before and discovering a number of "items of interest".
Mr Pettiford said Gympie detectives were contacted by people who knew Mr Saunders and had suggested his death might not have been an accident.
Mr Saunders and the two accused males were helping a female friend clean up her Goomboorian property as an "act of goodwill" when the horror incident occurred.
It's believed the woman, who had recently lost her husband and was in the process of selling the property, had asked the men for help. Police do not believe the woman had anything to do with Mr Saunders' death
The men had been helping the widow for the past three weekends and were minutes away from finishing for the night.
Questions were raised about the men using the shredder in the dark but Mr Pettiford said the incident, which occurred at 7.40pm, happened when it had only just started to go dark.
It was going to be the last day they'd use the shredder and help their friend.
Police said the woman was "extremely upset" and was helping them with their investigation.
In November, Gympie Police Acting Inspector Paul Algie said the circumstances were "horrific".
"I went out there this morning to speak to officers from Brisbane and I'd have to say it's one of the worst incident scenes I've ever seen," he told the Gympie Times last year.
"There was nothing that could be done to save this gentleman."
It was first believed Mr Saunders was working with his two friends on the property as a favour to the woman who lived there when he became entangled in branches, tragically getting dragged into the woodchipper.
Mr Roser and Mr Koenig first told police they had tried desperately to save him after realising Mr Saunders had become entangled.
"It was actually quite horrific. His friends discovered him as he became entangled and attempted to extract him from the shredder and were unable to do so. So they're obviously quite traumatised now," Insp Algie said in November, immediately after the incident.
All three have had their matters adjourned to August 3 for a committal mention.
— With wires
