Let me start by saying my 3 star is based on comparison to other places I go and not an indication of poor quality or bad service. The overall quality was good, and the service was excellent. So why the low rating?
I think other reviewers must not get out a lot. Grass Roots is just average for similar places and overrated compared to like priced restaurants. For the same cost you can go to Lons at the Hermosa Inn and get much more value. Grass Roots does a good job and you probably will not be disappointed but they are over priced for what they deliver.
I have been there twice, once mid afternoon for Key lime pie and coffee and this time for lunch with business associates for lunch. The Key Lime pie was wonderful but not worth that cost, the wait staff was fun and attentive, and the coffee was good but cold on delivery. And we were the only people in the place. But it was about 3:00 pm so that is not an issue.
Lunch was OK. I ordered coffee from a very fun waitress as did my associate. The coffee had to be returned because it was again cold. To their credit they remade fresh coffee and their coffee is good. I asked if they had whole chilies and I was told they have Poblano chilies so I asked them to put a chili on a burger and serve it with no bun. The waitress came back and said they could not give me the chili but they could put Halapenos on it. I declined those and asked to just serve their normal burger with no bun medium well.
I got a diminutive burger, like a fast food place, cooked hard. It was very good but for $11.00 I anticipated something more substantial. Compared to let's say Rosy McAfery and their wonderfull pub burger. Much bigger, much better and half the cost.
The fries are really good and I ate every one of them.
All four of us got fed, the food was good, the atmosphere was conducive to conversation and the service was excellent but the place was not even half full at lunch and it was expensive.
So you will not hate it, but you can get much more value at several places in that area because 20th Street and Camelback is cluttered with good to wonderful restaurants.