The speed limits in Italy are 50 km/h (50 mph) in built up areas, 90 km/h (56 mph) outside built up areas, and 130 km/h (86 mph) on motorways.
The motorways are the A roads, the main non-motorway roads are the SP roads, and the smaller main roads just have road names.
The motorways signs are in Green, the SP road signs are in Blue, and signs for the smaller roads are white.
The motorways are all of a high standard but they are all toll roads and they are very expensive to use, they cost about double of what they cost in France and Spain to go a similar distance.
Italy is also famous for it’s Alpine passes so there is not much else to say about the Italian roads as far as biking goes except that some of the coastal roads South of Rome have spectacular views.
Petrol is usually about 30 cents per litre more expensive on the motorways than on the other roads and at the time of writing it was about 1.90 Euros per litre.
I do not remember seeing many speed cameras in Italy nor a lot of police patrol cars on the motorways.
My personal favourite Italian roads are those in and around the are of the Italian lakes but during peak holiday season they can be very congested.
I did not buy a SIM card for a mobile phone whilst I was in Italy so I have no information about how to do this.