Roberts was delighted when he learned his teammate has handed the greatest honour in rugby and reckons the experienced contenders, who narrowly missed out, will provide invaluable support.
"When we turned up at training Tuesday morning and realised he (Warburton) was not there, we put two and two together," said Roberts.
"Personally, to see a guy from Cardiff, who has come up through Cardiff schools rugby makes me massively proud.
"I have a huge amount of respect for Sam and what he has achieved. It's a unique accolade in rugby. We can only imagine how he is feeling. That chance is so unique. It is a huge moment for Sam and his family.
"We will all get behind him. Warren has made no secret of his admiration for how he leads from the front and how he leads on the park, and I am sure all the old guys like Brian O'Driscoll and Paul O'Connell will get behind Sam and help him towards the ultimate goal of winning the Test series in Australia."
On a personal level Roberts was overjoyed with his own inclusion and relieved to have made it but he was quick to pay tribute to his Wales team-mates missed that missed out.
"This is probably better than four years ago. For some of the boys it is our second tour," said Roberts.
"It's an amazing feeling, a different feeling to the one four years ago, more one of relief this time around. It's the pinnacle for any player.
"It's unbelievable to have this number of Welsh players. It's testament to not only the Welsh national team and our success in the Six Nations but the coaches and staff at the regions. That is where we have trained every day leading up to this.
"But on behalf of all of us, our commiserations are with the guys who didn't make it, people like Ryan Jones, Dan Biggar and Ken Owens. That could easily have been any of us. Our thoughts are with them."