"It's simply all about the first game for us at the moment," said the Cardiff Blues star.
"To win against them would be a great start and we aren't looking beyond that.
"The preparation has largely been done and we've been pleased with the warm-up games and we have done well in parts.
"But that counts for nothing now. The World Cup is all that counts and the hard work starts now, building towards that first game on September 11.
"The game has all the ingredients to be a classic.
"South Africa haven't changed the way they play much in the last three years and they don't lose many games."
With his regular presence in the Welsh midfield it is easy to forget that the competition will be Roberts' first taste of World Cup action.
Back in 2007 Roberts was watching the tournament back home in Wales and as he prepares to play his part in rugby's showpiece event this time around he has revealed the honour of playing for his country.
"In 2007 I was probably watching the game with the boys back home," he added.
"It's crazy to think what has happened for me since then, the most amazing experience of my life.
"Wearing the Welsh jersey is something very few people get to do and you need to realise how privileged you are to wear it and how people would give their right arm to do so."