...uuhhh... agreed with our Italian contributor... among others.
While driving in Italy is no more dangerous than in the U.S. .... ... driving in Rome is like driving in New York -- both of which are markedly more dangerous than Santa Margherita or Gainesville, Florida (or Gainesville, Texas... or Gainesville, Alabama... or whichever Gainesville you are from).
That's a pretty long ride on the back roads. Are you an experienced motorcyclist? If not, do as another said and do that trip in a car. Scooters are designed for short, in-town, trips --
-- it's about 80 km, over an hour, by car on the autostrade Florence to Siena, then another 240+ km and 3 hours to Rome. The back-road motorcycle friendly route is over 400 km -- and I'm not sure a scooter is up to that task.
.
.
.
EDIT: To find a realistic expectation, I used ViaMichelin for directions, but asked for a Bicycle route. Florence to Siena is actually quite do-able, at 62 km and 4 hours. Siena to Rome on the bicycle friendly route is 216 km or 15 hours. A scooter (if allowed on all those routes) could probably do it in half the time -- but 7 hours on a scooter? I'd rather spend that time in Siena.