I was recommended Vitaminas24 by the owner of the apartment I was renting during my holidays in Rome. It's a really cool place in Pigneto area and I believe it's the only proper vegetarian place in the neighborhood.
They have quite a nice selection of fruit and veggie juices which was the main reason I stopped by on one of the afternoons. The menu is only in Italian, but the guys working there took their time to explain what is what and were very helpful. I also had a gluten free cake for take away and it was absolutely delicious. Portions for veggie burgers and other lunches looked decent and fairly good value.
The only downside was that I was planning to come back another day for dinner (around 8pm) but they were closed despite the fact the guy working there said they are usually open till midnight. I think since they are a small business, they probably open when it suits them best.Pros: inexpensive, good selection of juices, cool vibe
Cons: not clear opening hours, no English menu