First train timings at Roma Travestere to Pompeii

You can plug in a date within the next seven days to see the regionale choices on Trenitalia. Tickets never sell out for regionale trains. The train from Napoli Centrale (1.25 hours from Roma Termini) is a Circumvesuviana train, departs every 30 minutes or so from its own station downstairs from Napoli Centrale (buy your ticket from the Circumvesuviana ticket office before you go downstairs). You want the train going to Sorrento, the Pompei Scavi stop is about 40 minutes from Napoli. There's a subway-type map of stops on the train wall, stops are not announced. Hold on to your ticket in case you need to show it at the exit.

Thank you.

For a weekday trip, the timings within the next 7 days should be the same as the timings in June right? Do the trains arrive on time? I'm afraid if the first train is delayed I'll be unable to board the main train to Naples.

You can always take a bus to Termini. Or a taxi, if you fill a taxi.

Most trains are one time, some are not. There could be all sorts of reasons a train is late, from vandalism to a break down. Impossible to predict. I never assume I will be late but often catch an earlier connecting train if I am catching an important train. Not just in Italy, everywhere.

I work on trains in England. Virtually all the trains I work on are on time. If I have to get somewhere as a passenger and the timing is important - like an airport - I always build in a cushion.

Without looking, I believe that the first Freccia from Termini is at 0735, the first Italo from Termini or Tiburtina is about an hour later. The earliest trains to Napoli Centrale are Regionale and InterCity, and one InterCity Notte. They are slower but still get you there a bit earlier.

How early do you want to start?

As said above, you can always get a Regionale ticket - always. If the train is crowded, push on (politely) and stand.

How to Look Up Train Schedules and Routes Online gives you the DB train schedule link and tips for using it. This is not tied to which tickets are currently for sale. All schedules are published through June 13 and some later. They are also easy to print from this site.

trenz,

I suspect your best bet will be to depart from Roma Termini, as you'll have a great choice of trains. According to the current schedules, there's a Regionale departing at 05:40, arriving Napoli Centrale at 08:12 (time 2H:32M, current fares €11.80 PP). After that there are InterCity departures at 06:26 and 07:26 (time 2h:03M, current fares at €26, using an arbitrary day next week to check).

When you arrive at Napoli Centrale, walk downstairs to the Garibaldi station and buy tickets for the Circumvesuviana, which will take you to the Pompeii Scavi station. When you're finished touring, take that train back to Naples and do some sightseeing there.

The Circumvesuviana ticket booth is on the main train level, before you go down the stairs.

Thank you all for your help! It's really much appreciated :)