Justice Anthony Besanko launched a scathing criticism against the former SAS corporal who had motives to lie about the events in Afghanistan.
In his summary judgment delivered on Thursday in the Federal Court, Justice Besanko dismissed the cases against The Age, The Sydney Morning Herald, The Canberra Times and three journalists over reports published in 2018.
"I find that (Mr Roberts-Smith) was not an honest and reliable witness," the judge said in the full judgment published on Monday.
The ex-soldier sent threatening letters to witnesses who ultimately gave evidence against him at the defamation trial by hiring a team of private investigators to find out their addresses.
"The sending of the letters may constitute a criminal offence of attempting to pervert the course of justice ... or using a postal or similar service to menace, harass or cause offence," Justice Besanko said.
Mr Roberts-Smith used burner phones, used encrypted apps and buried USB sticks in a lunchbox in his ex-wife's backyard once he knew he was an important subject of an investigation by the Inspector General of the Australian Defence Force.
The activity to hide his tracks took place as the media reported truthfully on war crimes committed while Mr Roberts-Smith was deployed in Afghanistan.
During a 2009 Easter Sunday raid on a compound codenamed Whiskey 108, Mr Roberts-Smith machine-gunned an unarmed prisoner in the back, taking the man's prosthetic leg back to Australia to use as a beer drinking vessel.
Mr Roberts-Smith stood silent as a rookie soldier was ordered to execute an elderly Afghan prisoner so he could be "blooded".
Justice Besanko called the former SAS corporal's denials of these incidents "highly improbable" after hearing from independent witnesses with no reason to be dishonest.
"The applicant has motives to lie, being a financial motive to support his claim for damages in these proceedings, a motive to restore his reputation which he contends has been destroyed by the publication of the articles and significantly, a motive to resist findings against him which may affect whether further action is taken against him."
Justice Besanko found one of the newspapers' central claims - that Mr Roberts-Smith had kicked an unarmed and handcuffed man, Ali Jan, off a cliff and then ensured he was shot - was true.
As evidence of his guilt, Mr Roberts-Smith attempted to cover up the unlawful killing at Darwan in September of 2012 by removing Mr Jan's handcuffs and planting a radio alongside his lifeless body before he was photographed.
Mr Roberts-Smith then told fellow SAS soldiers who witnessed the incident to stick to an approved story that Mr Jan was a spotter they killed legitimately.
In accepting the newspapers' claims, Justice Besanko rejected Mr Roberts-Smith's account of the incident, which was riddled with a number of improbabilities.
In October, 2012 in the Chinartu district, Mr Roberts-Smith ordered another soldier to execute an unarmed Afghan prisoner being interrogated after his troop discovered a fake wall cavity filled with weapons, including rocket propelled grenades and warheads.
"Person 12 then gave instructions to an NDS-Wakunish soldier who then shot the Afghan male in circumstances amounting to murder," Justic Besanko said.
"(Mr Roberts-Smith) was complicit in and responsible for murder."
Reports Mr Roberts-Smith bullied soldiers and assaulted prisoners were also true.
This included an attack on a prisoner in Deh Rafshan in March 2010 where, after soldiers detained an Afghan male who posed no threat, the war veteran entered the room and launched three to four "quick-fire punches" to the man's head.
"It involved the unnecessary application of physical force and was an unlawful assault," Justice Besanko said.
The three media companies will be seek costs for defending the lawsuit, with the total legal bill estimated to be $25 million.
Mr Roberts-Smith was last seen in Bali.
He resigned from his role as general manager of Seven Queensland on Friday.
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