I went to Rome a couple of weeks ago. Connecting from a domestic to intl is not a big problem. No need to reenter security. The other direction (intl to domestic) takes much more time. (clearing immgration,customs, then rechecking checked luggage upstairs & then reentering security). Hope you have almost 2 hours on the return--may take from 1 hour (optimistic--having only carryons & getting lucky) to 2 hours. It took me 1.5 hours to get to the domestic gate. I had a 3.5 hour layover but I was in Envoy so I had use of the club.
