The problem I find with airports is that GF stuff is limited at best. Rome airport took this to a new level. All I could find were those schaar squidgy dry as a rock buns and a packet of crisps. Previously there was a McDonalds ground side but that has now moved to after the initial security check at departures.
Luckily we were staying at The Hilton the night before we caught our flight and the restaurant staff were brilliant. They told me they could prepare several GF dishes.
If you are travelling through the airport without stopping-off then McDonalds is your only option. You can find it after the first level of security.