Pompei and Naples

Sure....but a loooong day. Leave Rome as early as you can, transfer to the Circumvesuviana train in Naples for Pompeii Scavi, tour the site for a few hours, head back to Naples for the later afternoon and evening, then back to Rome. The fast ES trains take less than two hours, but you'd have to cab it back the 2 miles to get from Naples Garibaldi station to Centrale Station to catch the Circumvesuviana. Other trains take about 3 hours and run to Centrale. To reduce time, you could take the Circumvesuviana just to Herculaneum (Ercolano) and see the ruins there (more mosaics still intact, a lot more compact, and right in the shadow of Vesuvius) then head back to Naples.