For Austria and Italy, if you really want a SIM roaming from Australia, you want a '3' SIM as 3 have no roaming charges if you connect to the 3 network in Italy and Austria. 3 Have no network in France.
Vodafone pricing is marginally discounted if you roam on a Voda network, but not much - I wouldn't recommend it!!! You can select from two roaming options with Voda:
Traveller Vodafone Traveller or
Voda World Vodafone World
Vodafone World is the option that gives slightly lower rates if you roam on a Voda network. Still doesn't compare to the 3 offering.
I would recommend getting a local prepaid SIM in each country.