Is there a shop at FCO or Roma Termini that sells SIM cards?

My itinerary is as follows:
Italy (7 nights)
Spain (2 nights)
Italy (1 night)
Switzerland (2 nights)
UK (3 nights)

I would be using the SIM card mostly for voice calls to/from these countries as well as the USA, and maybe some texting.

What do FT-ers recommend? How much do the card and calls cost, in Italy and after I leave Italy? I don't know any Italian, so I can't tell from the Vodafone and TIM websites.

Thank you!