Venice to Sorrento

There is also the commuter train between Sorrento and Naples, I don't know time difference--it may also depend on where you are staying.

The ferry to Sorrento will mean taking the subway or taxi from the train station to the ferry port. It will be more convenient and likely faster to take the Circumvesuviana train or Campania express train from Naples to Sorrento. A driver from Naples is also an option, cost is like over 100 Euros.

For your purpose, the ferry would be very inconvenient to use. As is, it will be a long day - close to 8 hours and the ferry could add another hour or more. Take the train to Naples, and change to the Circumvesuvianna. It is a so so commuter train but it works.

PS -- The fastest train I see between Venice and Naples is 5 hrs, 23m. Nor sure where Robert (next posting) is getting "about 4 hours" for the run to Naples.

The Freccia train from Venice to Naples is about 4 hours. But, it is very comfortable and the scenery is great (hey, it's Italy!). Depending on when you book, and what class of service you book, I think you'll find the fare very reasonable. The ferry to Sorrento is wonderful - it's relaxing, it's scenic, it's refreshing, it's faster than the Circumvesuviana commuter train. Reversing the process to go to Naples is easy by ferry or by train and then on to Rome by Freccia. The ferry schedule may not be the most convenient but if there is a wait, there are places to sit, to eat, to drink, to wander (it's flat by the dock so pulling luggage isn't too awful). To get to the ferry from Napoli Centrale station - take a taxi, it isn't too far.

It will take you about 7 hours taking the train from Venice to Naples, then about 2-3 hours from Sorrento to Rome by train. We were in Rome in May, going to Sorrento and were looking at the Ferry option. The weather prevented us from taking that option. We took the train and the transfer from Sorrento to Naples and the Naples onto Rome is super easy, just a short walk (less than 5 minutes).

Train to Naples, then either the Circumvesuviana or Campania express (April thru October) commuter train is the easiest, and likely fastest. Or hire a private car service from Naples ( the most expensive option). Or take the ferry which would require a taxi from the train station, and is weather dependant.

From Sorrento to Rome, same options in reverse.

The fastest train, non-stop, from Venice to Naples appears to be 5 hours and 22 minutes long on
Trenitalia.
Italo is about the same, just very slightly cheaper.

S J all trains between Venice and Naples make 3 stops (Bologna, Florence and Rome) or more.
A no-stop train would never break-even.

I cannot comment on Venice to Sorrento as my arrival in Sorrento originated from Florence but I did go Sorrento to Rome recently via train.

This may not be the best/fastest but to give you an idea of timing Sorrento to Rome via trains here is what we experienced:

1:20pm - departed Sorrento via campania express (not the most convenient given limited options) but timing worked for us.

2:30pm (Approx) - Arrived at Napoli centrale.

3:40pm - took a direct freccia to Roma termini

5pm - arrived in Rome

Total time from Sorrento to Rome 3 hours 40 min.

Granted - we had an hour and 10 minutes connection time in Napoli .. you could do with shorter connection time assuming there are no delays on your train from Sorrento to Napoli …
circumvesuviana commuter train runs on the same line and has more options than CE and takes about the same amount of time.