See the below info from the webehigh website:
"For cheap Weed (in buds) but still good quality, you should check out Piazza di Santa Caterina della Rota. To get there, just go on Campo de’ Fiori and ask where Caffé Perù is (That place is awesome if you don’t want to pay insane prices for your beer/cocktail). You’ll be there in seconds (google streetview –>
http://goo.gl/maps/te3GU) There will most likely be one or more guys sitting in front of the church’s doorstep. If he’s not there, he might be sitting on the doorstep of the building on the left. Go there and ask the guy/guys for weed. He doesn’t bag his weed so be prepared and bring some kind of container (empty cigarette pack for example). The price is about 10€ per gram, but he’ll overweight the shit out of it as he doesn’t put it in bags.
If you’re looking for hashish, Ponte Sisto (Piazza Trilussa) is the right place for ya. It’s pretty standard quality though and the Police likes to be in the Piazza, so make sure they’re not around! Just ask people on the bridge for weed. Some might ask you to do some roleplaying (go away from the bridge and then act like you’re meeting a good friend and do the exchange). Price is 10€ for 1g there too."
http://webehigh.org/rome-italy/
