connecting flight time allowance

If you are connecting through to Rome, and your luggage is checked, you will not have to go through customs in Frankfurt. In fact, I've flown into Frankfurt half a dozen times with carryon luggage and never had it checked in customs. If you do go through customs, there will be a line marked "nothing to declare", and you just walk out of the room through that line. Immigration could take some time if several planes just landed, but two hours should be plenty of time. Luftahansa uses three concourses in Frankfurt (A, B, & C). If your connecting flights are on different concourses, you will have to change ,and it will probably mean going through security again. Go here to see a map of the airport and to find the concourses used for your flights.

No customs in FRA. Customs for you will be at your last destination (FCO). Your baggage will go to the Rome plane directly and you won't see it until you arrive at FCO at the baggage claim. In FRA you will have to go through EU Passport Control (immigration) right after deplaning. You will have to walk to your Rome flight gate. It's likely a long walk from arrival gate (likely concourse C) to departure gate (likely concourse A) at least in my multiple experiences at FRA. You will also need to go through security check again ( metal detectors) before going to the Rome flight gate. Two hours are more than adequate unless your flight from BOS is delayed. My layovers to Florence are generally 1hr and 30min max and I've never missed the connection in so many times I've gone through FRA.

Yeh, just got back from a Geneva RT with a 65 minute change in Zurich. No sweat. Everyone gets their passport stamped on entry to Schengen zone.