Veteran centre Contepomi, 35, has been recalled to the Argentina starting line-up for the Millennium Stadium Test against Wales, having sat out the Pumas' Rugby Championship campaign.
It will be the Stade Francais back's 79th cap for his country, but his return will see him face the responsibility of coping with the wrecking ball-like abilities of Roberts, who is back in the Wales team having missed the tour of Australia after undergoing knee surgery.
Contepomi will be giving away four inches in height and around 30 pounds in weight to the Cardiff Blues centre, and while he is relishing the task ahead, he knows just how difficult a test it will be.
He said: "It's a huge challenge. It's like climbing Mount Everest.
"Jamie is one of the best centres in Europe and one of, if not the best in the world.
"As a player you want to play against the best and to have that challenge on Saturday and I'm looking forward to it.
"He's a great guy and it's delightful to watch him play but it's not so good when he's in front of you.
"Wales have a lot of important players and we see them as a unit. But Jamie has that extra x-factor. He has that experience now but we're trying to analyse them as a unit. We're trying to develop our game more than thinking about Wales and want to be more offensive."
The opening fixture of the Pumas' tour, which also includes games against France and Ireland, sees Contepomi return to the venue of one of his most treasured rugby memories.
Contepomi is the only survivor from the Argentina side that stunned Wales 30-16 in Cardiff in 2001.
The former Leinster man contributed 25 points that day as the Pumas began their climb to claim a place at international rugby's top table.
"It's one of the great memories of this team but I am the only survivor. For many of the players from that game, and every time we meet up to catch up, we always remember that game," he said.
"It was one of our biggest wins away from home and gave us the confidence and mentality to look to win every game, no matter where.
"Wales is a rugby nation that we love, we've always been very in touch since the 1970s when we nearly beat them but lost in the last minute.
"It's one of the places you always want to play and I was so lucky to be part of the team that beat Wales at the Millennium Stadium.
"I remember the try I scored and enjoyed it. It was great but it was good for the team. The whole tour was great, that gave us the confidence to beat Scotland at Murrayfield."
But Argentina's record points scorer was cagey when asked what the chances of a repeat result are this weekend.
He said: "We are looking forward to the challenge and are well prepared. Most of the players have been together for three and a half months in a tough tournament.
"It's much easier to come together, we're not starting from scratch like in the past. But you can be well prepared, the only thing that counts is that 80 minutes.
"We would love to beat Wales but it's important that we perform properly. We know we're playing a quality team, the team that has developed the most in the last two years."
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