my wife and I like to travel the countryside and just stop where ever we are for the night. Is this possible to do in June? We will have 21 days of travel from Rome to Venice.
Easily.
I agree. But looking for a place can takes some time each day, so I'd certainly want to hang out in a few places for several nights and do day trips.
Often, we'll stop somewhere for lunch and decide we want to stay there. I'll go to the local tourist information offices and ask who has vacancies. They can call ahead for you.