Elsom was suspended after he was found guilty of tackling Springboks captain Victor Matfield in the air at a line-out during last weekend's 27-15 win in Durban.
However, that decision was overturned today, freeing up the 25-year-old to take his place at Coca-Cola Park.
Timana Tahu will make his Wallabies starting debut in the match after he was called in to replace the injured Berrick Barnes at inside centre.
Tahu's selection caps a meteoric rise for the 27-year-old dual-code international after he converted from rugby league earlier this year.
Australia coach Robbie Deans has made five changes from his side that ended their eight-year winning drought in South Africa last weekend.
The other changes see full-back Adam Ashley-Cooper return from a broken hand to regain his position from Drew Mitchell, Hugh McMeniman returns in the second row for the injured Daniel Vickerman, while Phil Waugh and Tatafu Polota-Nau come in for George Smith and Stephen Moore respectively.
The game is a dead rubber with the destination of the Tri-Nations trophy to be resolved when the Wallabies host New Zealand on September 13.
Deans, however, claims there is still plenty riding on the game as the Wallabies go in search of their first back-to-back wins in South Africa in 45 years.
"Saturday still has huge significance - both in terms of momentum in the Tri-Nations; but also as far as the development of our group as a whole is concerned," he said.
"By winning in Durban last weekend, we have presented ourselves with an opportunity - to win back-to-back Test matches in South Africa - which is not only rare in an Australian context, but is also historically significant across the game in general."
Australia team: Adam Ashley-Cooper, Peter Hynes, Stirling Mortlock (capt), Timana Tahu, Lote Tuqiri, Matt Giteau, Sam Cordingley; Wycliff Palu, Phil Waugh, Rocky Elsom, Hugh McMeniman, James Horwill, Matt Dunning, Tatafu Polota-Nau, Benn Robinson.
Replacements: Stephen Moore, Al Baxter, Dean Mumm, George Smith, Brett Sheehan, Ryan Cross, Drew Mitchell.