It would take about 2 hours at the latest.
From Sydney to Rome, it is about 16315 kilometres (10197 miles), and a flight would take about 17 hours and 57 minutes. However, 20 hours is more accurate.
It takes 13 hours.
the flight takes about 9-10 hours
If you live in Okinawa, I suggest connecting through Tokyo. From there it would be 10 hours.