As his patrol remained pinned down in an orchard by relentless enemy gunfire, 32-year-old Cpl Roberts-Smith stormed two of three enemy machine guns and killed their crews.
Cpl Roberts-Smith's courage was found to be instrumental in his patrol's victory over a Taliban force three times larger and earned him the British Commonwealth's highest military honour, the Victoria Cross.
"I think for everyone there, including myself, what's going through your mind is you just won't let your mates down," Cpl Roberts-Smith said after he was awarded the medal yesterday at his Special Air Service Regiment barracks in the West Australian capital, Perth.
"I saw a lot of brave men do a lot of brave things that day," he added.
He now has one of only four Victoria Crosses awarded in the almost decade-old war in Afghanistan. Fellow Australian soldier Mark Donaldson was awarded his in 2009, New Zealand commando Willie Apiata in 2007 and British paratrooper Bryan Budd was given a posthumous award that same year.
Donaldson and the only other surviving Australian Victoria Cross-winner Keith Payne, who earned his in the Vietnam War in 1969, attended Sunday's ceremony.
Cpl Roberts-Smith, who received Australia's Medal of Gallantry in 2006 for an earlier tour of duty in Afghanistan, is now Australia's most highly decorated soldier.
His actions last June 11, during the height of Afghanistan's so-called fighting season, showed "most conspicuous gallantry" and "total disregard for his own safety," his citation said.
By breaking cover and charging the Taliban position, Cpl Roberts-Smith deliberately drew enemy machine gun fire away from his pinned down patrol and they were able to return fire. He charged to within 65 feet of the enemy during the ensuing gunfight.
Prime Minister Julia Gillard, who is struggling to sustain public support for the Afghanistan war as Australian casualties have mounted to 21, was among the dignitaries who attended today's award ceremony.
"You went to Afghanistan a soldier, you came back a hero," the Prime Minister said. "Our nation is enriched by you being among our number."
Australia has the largest military commitment in Afghanistan of any country outside Nato, with 1,550 Australian troops there.
The Perth-born father of twin daughters was given the award for his conspicuous gallantry during a fierce six-hour battle in the Shah Wali Kot area of northern Kandahar last June.
He single-handedly neutralised several enemy machine gun positions during the battle that left more than 60 enemy dead.
His Queensland-born wife Emma, their five-month-old twins Elizabeth and Eve, father Len, who is a retired Major-General and former Judge Advocate General of Defence and WA Supreme Court judge and younger brother Sam, a baritone with the Australian Opera, along with political and military leaders and dozens of his SAS comrades, witnessed the ceremony that also recognised the gallantry of several other soldiers from the elite Special Air Service Regiment.
Britain's Corporal Bryan Budd, of the 3rd Battalion The Parachute Regiment (3 PARA), was posthumously awarded the Victoria Cross for acts of "inspirational leadership and the greatest valour".
He is only the second recipient of the award in 24 years.
Corporal Budd's wife accepted the award on his behalf, which he received for two separate acts of exceptional valour while deployed in southern Afghanistan in July and August 2006.
Karzai settles parliament delay
Afghan President Hamid Karzai has agreed to scrap a one-month delay in convening the new parliament, ending a stand-off with members that had threatened to spark a constitutional crisis.
Mr Karzai had ordered the opening session to be postponed to allow more time for a special tribunal to investigate allegations of fraud in September's parliamentary election.
That set off an outcry among members of parliament and drew heavy pressure from the United Nations, the United States and other world powers for Mr Karzai to resolve the dispute.
After hours of discussions at the presidential palace, Mr Karzai agreed to open the legislature on Wednesday, according to two of the members of parliament involved.