Need advice on flight connections from RDU to FCO (and back)

First off, no matter what the historical data, you could be unlucky, so that's just a fact of life.

For the outbound, the opposite view from your preference is that getting across the pond
is better than being stuck in Charlotte. So if there is a transatlantic flight out of RDU that
suits your needs, I would take that flight. Most likely through London for you on AA.

If you do go thru Charlotte and want to be conservative, check the other intl AA flights
out of Charlotte that leave after your flight to Rome. Getting across the Atlantic is
the main priority.

For the return, do you have Global Entry? Either that, or using the Mobile Passport app
will help you get through immigration (Customs is not the issue usually, Immigration is)
faster. If you have checked baggage, there is a bit more risk since you'll have to wait
at baggage claim to retrieve your bags and recheck them for the connection. But 2:07
should be fine; it's a legal connection, anyways.

Again, if you can connect in London and fly home direct to RDU, then your concerns
about Immigration delays go away since you're at your home airport when you have
to deal with it. Or, check and see when the flight back to RDU from either PHL or CLT
after the one you book is; that's your backup plan, and a shorter wait is better than a
longer one.

I have offered a few other times with these questions to also consider the potential for one or even both of your choices to have their times change, especially when purchasing this far ahead.
I always prefer at least 3 hours, especially if international, but that's personal preference. However, my last flight was delayed enough that I would have missed the connection if that next plane hadn't also been delayed.
And now, getting ready to fly home on my current overseas trip, it was the same scenario on the way here. Also, my carefully chosen seats disappeared due to a change not only in departure time but also aircraft configuration!
Regardless when you decide, do continue to monitor those purchased flights/seats in the months before you depart.

If you buy this all on one ticket, you are covered should you miss a connection. The airline has to put you on the next available flight at no extra charge to you.

I fly AA out of RDU a great deal. (I'll be on an AA flight out of RDU in a few hours.)

Changing planes in London will mean a change of airline and a change of terminal. It's not difficult, just time consuming. AA has a nonstop from RDU to LHR so check the connection there. Even if you miss the connection, BA, their partner airline, has a few daily flights from LHR to FCO. (Changing terminals is done via an airside bus. You don't have to go through immigration in London.)

Your bag should be tagged throught to Rome so you won't see it until Rome. No need to get it in London.

On the return, how much time you need really depends on a lot of factors. If you have Global Entry, you will save a lot of time. If not, download Mobile Passport Control (MPC) to your phone and learn how to use it. This will also save time.

However, since you said you have a checked bag, you will have to retrieve it at your first port of entry into the US and then recheck it in after Customs. (There is usually a check in area as you exit customs.)

For either PHL or CLT, check to see how many more flights the airline has to RDU after your scheduled landing at either airport. Go with the one with more choices should you miss the connection.

Why not just drive from Raleigh-Durham area to CLT?

Both RDU-to-CLT and CLT-to-RDU are around 2 hours layovers according to the original post. Depending on where you actually live, the actual drive from RDU-CLT per google is about 2.5 hours.

The driving time vs the layover time and other factors would be awash.

Driving allows you to leave exactly when you want to from home and not worry about any flights to/from RDU connecting flights.

While not a big fan of driving I have done the drive from the Triangle area to CLT to catch a direct flight and it is not that bad (depending on the time of day). Took a break on the drive to pick up snacks for the flight and parked in a remote lot but getting to the terminal was easy with the shuttle. Might be worth considering.

When I posted yesterday, flying out of RDU seemed like my best option due to a personal / logistical issue with driving to CLT. Fortunately, I figured out a way to make it (CLT) work. And so, I literally just booked a direct flight from CLT to FCO. Yay! 😊 Thank you, everyone, for your input! You all are always so helpful.