The 25-year-old Roger, who won a first cap off the bench against England in July, comes in as flyhalf cover for Tomas Albornoz, who will miss the trip after hurting his hand in last Saturday's historic first home victory over New Zealand in Buenos Aires.
The 29-year-old Calles replaces veteran prop Nahuel Tetaz Chaparro, who decided to end his lengthy international career after Saturday's victory.
"We closed out the year at home with a great win against the All Blacks, which gives us a lot of energy for the challenging tour ahead," said coach Felipe Contepomi as he named the squad on Tuesday.
"It's important that over the next five weeks away from home we can continue to build as a team and grow day by day.Â
"We are very grateful for the support we've received over these past few weeks in Argentina and are confident we'll find many fans cheering us on in Australia."
The two clashes with the Wallabies are in Townsville on September 6 and Sydney on September 13.
Argentina then travel to Durban to take on South Africa on September 27. Their final clash of the Rugby Championship against the Springboks will be at Twickenham on October 4.
Argentina squad:
Backs: Simon Benitez Cruz, Mateo Carreras, Santiago Carreras, Santiago Chocobares, Lucio Cinti, Bautista Delguy, Benjamin Elizalde, Gonzalo Garcia, Rodrigo Isgro, Juan Cruz Mallia, Ignacio Mendy, Agustin Moyano, Justo Piccardo, Geronimo Prisciantelli, Nicolas Roger
Forwards: Ignacio Calles, Francisco Coria Marchetti, Juan Martin Gonzalez, Santiago Grondona, Marcos Kremer, Pablo Matera, Franco Molina, Julian Montoya, Joaquin Oviedo, Lucas Paulos, Guido Petti, Tomas Rapetti, Pedro Rubiolo, Ignacio Ruiz, Joel Sclavi, Mayco Vivas, Boris Wenger.
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