First things first: depending on which airlines have reward seats available, you’ll need between 512,000 and 556,000 points for 2 return Business seats to Rome. So your first priority needs to be getting enough points so you can snaffle the seats if/when they do become available.
Alternatively you could book one-way reward seats now, and either pay for the flight in the other direction (safer) or wait until you have enough Qantas points to book the second trip (risky, because seats might not be available on the dates you want).
In my limited experience, reward flights to Milan are a little easier to come by than flights to Rome, so if you’re coming across some dead ends with Rome, Milan might be an option or even Venice. If flights are really hard to come by, consider anywhere in Europe and hopefully you’ll be able to purchase a cheap flight to Rome from wherever you end up!
Hope this helps a little and all the best!