Earlier this year, AFTER immigration at FCO, I experienced it to be a very brisk 25 minute walk from where my international flight landed at FCO to the terminal where I was boarded an Alitalia flight to Trapani. Doing that in reverse, with stops for passport control and security could make for a tight connection. There is also this factor: From time to time, with no warning, Mt. Etna will belch enough ash into the air to cancel all flights in/to Catania for a few days. Doesn't happen often, but does happen enough to have affected some travelers on a RS tour of Sicily last year (as noted in this forum). Just sayin'. For this reason, when Sister and I were departing Catania to connect in Rome for our onward flight home (to US), we booked a couple of nights in Rome, just to be on the safe side. I would concur with the suggestion to book your last night in Rome, so that you don't have to rely on Alitalia's timeliness and Mt. Etna's quietness to get you onto your homeward flight. There's also the issue that a 9:55 am departure doesn't mean you can be at the gate at 9:50. Generally boarding for international flights is cut off some 30 minutes or more before actual departure time. (Correct me please, someone, if you've experienced this differently.) That Catania-Rome ticket probably cost you approx. $100. Is it worth the gamble? If you've already booked all of these tickets: you could probably make this connection, but I am too cautious a traveler to bet on it myself.