If you add a roaming package, using your phone in Australia will use the minutes from the roaming package. If you don't add a roaming package, you will be charged $1.50/minute. This is what it costs to use your phone on a network which is not owned by koodo, and will be the same regardless of which country you are calling.
Roaming and the international save add-on aren't the same things. The international saver gives you better rates from Canada to the US but if you need to call from outside canada you need "roaming" packages that can be found here : https://www.koodomobile.com/help/travelling-outside-us