The witness codenamed Person 11 continued his evidence on behalf of his good friend on Thursday in the Federal Court about the final mission his troop conducted in 2012 in Afghanistan.
Another comrade dubbed Person 16 has previously testified that in November he detained Afghan prisoners in a Toyota Hilux and they were handed to Person 11's patrol commander Mr Roberts-Smith.
Person 16 told the court in February he distinctly remembers a "baby face looking young man" with a patchy beard who appeared terrified.
Barrister Nicholas Owens SC representing the media outlets being sued for defamation submitted the retired soldier would remember this prisoner.
"Do you recall one of the (prisoners) you collected ... was distinctive because he was an Afghan adolescent or young adult who was visibly shaking with terror."
"No I do not Mr Owens," Person 11 said.
He was then asked if the teenager was taken into a secured room by Mr Roberts-Smith who allegedly shot him in the head.
"That's not true."
It was also submitted an AK47 rifle was planted on the body to give the false impression he was armed at the time, but the witness rejected this.
Mr Owens showed him a photographic document he said identified three prisoners detained from the Hilux and taken back to Australian headquarters at Tarin Kowt for further questioning.
He showed another image of a fourth prisoner allegedly taken from the vehicle. Mr Owens said he was the Afghan adolescent executed.
"No I reject that," Person 11 said.
"I put to you the reason there is no photograph of the 2nd PUC taken ... from the vehicle is because that man was murdered by Mr Roberts-Smith in the compound."
"I disagree with that."
A PUC is a prisoner also known as a "person under control".
Mr Roberts-Smith is suing The Age, The Sydney Morning Herald and The Canberra Times over 2018 reports claiming he committed war crimes in Afghanistan including murder, and acts of bullying and domestic violence.
The 43-year-old denies all claims of wrongdoing, while the mastheads are defending them as true.
On Thursday Person 11 also denied the assertion he contemplated leaving Australia to avoid his fourth interview with the Inspector-General of the Australian Defence Force.
He did not intend to "skip" Australia but was considering sourcing "work opportunities outside the country".
The former elite soldier earlier confirmed that he declined twice to be interviewed by the Australian Federal Police, but denied he was trying to derail their investigation into alleged war crimes he is also accused of.
It has been alleged that Person 11 executed a handcuffed prisoner named Ali Jan after he was kicked off a cliff by the Victoria Cross recipient during a September 2012 mission in Darwan.
Both men deny all allegations of wrongdoing and say the dead man was a Taliban spotter lawfully engaged in a cornfield.
Another witness, dubbed Person Four, who was best man at Person 11's wedding, has given evidence that in Darwan he witnessed Mr Roberts-Smith kick the prisoner off a steep slope.
After hearing shots ring out Person Four said he observed Person 11 standing in a position to shoot before the radio was planted on the body.
After these allegations surfaced, Person 11 said he cut ties with his former good friend and mentor, but denied he was angry or felt betrayed.
The trial continues.
Lifeline 13 11 14
Open Arms 1800 011 046
23°C