Ciao Journorr,
You mean this Saturday or on a Saturday in October? Not completely sure on that...
if it is this Saturday, since it is high season, it gets tough but not impossible. If you're in Rome and don't have the car until Sunday, I'd stay in Rome. You can find last minute bookings on
Booking.com for Rome for this Saturday.
If you're coming in October, for a 1 night stay, I'd also look at the above link for finding a suitable place BEFORE you arrive..... you really want a place that rents rooms by the night and a hotel or small B&B would be the best solution.
The thing with finding places without a reservation here is the method:
- go from hotel to hotel to ask for any availability - they don't post signs outside
- go to the local tourism office to see who has let them know they have spots available for that night.
Nowadays, the internet is the better solution - you get to choose where according to what you like and your budget, not just from what's available. Good luck!