We will be staying on via Sistina near the Villa Borghese. In addition to water, we would also like to pick up a few things for a picnic and some snacks.

Does anyone know of some alimentaris, supermarkets, salamuris, etc. in the immediate area?

In Rome, each locality (quartiere) has at least one supermarket (open long hours including Sundays) and a few grocery stores open varying hours. So you needn't worry about getting essentials.

There's a supermarket at the bottom of the stairs leading to the Spanish Stairs Metro station, at the Via Veneto

hi mweiner,

you can find any no. of diferent businesses by using google maps.

google google maps.

Put in the address [ie via sistina, roma] you want to search.

put supermarkets into the business box.

print out.

repeat for delicatessens,etc.

regards, ann

We stayed on via del Tritone.
The supermarket we went to was here:

Google map of Rome, use 'Satellite'
Find via del Corso / via di San Claudio (one block north of Tritone)
See the bus terminal? Just to the right, the street is now called via del Pozzetto, then via del Bufalo. Right in here is a store, not much signage so pay attention.
I think this is the address:
Via Del Pozzetto, 124

Thank you all.

Google maps was excellent! found two very close by. One is a supermercati with good hours and cheaper prices!