Likelihood of me and bags making connecting flight

Assuming you are coming from outside the Schengen Area, then you will have to go through passport control (immigration) in Rome where your passport is checked (and if necessary stamped) for entering the Schengen Area. That could eat up 20-30 minutes on a good day. Rome to Germany is intra-Schengen, no passport control when you land in Germany.
Given that, chances, not good.

Plus "Assuming my flight to Rome arrives on time" - flying intercontinental, big assumption.

If both flights are on the same ticket, they are connecting flights. Contact the ticket issuer and confirm the ticket meets the minimum connecting time for Rome. And, perhaps work with them to get a later connection to Berlin (AirBerlin/Alitalia has Thursday flights to Berlin at 1405 and 2010). Plan on either you or your checked bag not making the original connection and ensure you have placed in your carry-on anything that you will need to get you through until the bag arrives (meds, toothbrush, necessary clothing, etc.) Good luck!

It is tight but -- our experience with Rome immigration is mixed. Three times we sailed right though with min delay. But one time took over two hours. However, they were going through the waiting lines and moving people with short connections at the head of the line - obviously added to our two hours. So if you hit a line, don't be shy about showing your board pass to an attendant and moving to the head of the line. I will curse you for awhile but that is how the game is played.

Thanks to all.

It is what it is. I just called Delta, and was told 65 minutes is enough time to make the connecting flight and was given the option to changing to a flight to Amsterdam for a connecting flight to Berlin that would arrive at 10 pm. I'll pass. If I miss the connecting flight in Rome, hopefully Delta will be able to find a more suitable later flight.

My intent is to check at the front desk a suitcase. Both flights are on the same ticket. If I try to carry on a smaller suitcase, I am afraid that, sitting near the front, I will be boarded in a later group and will have to check-in a carry-on, which means I may have to wait after exiting the plane.

I was in similar situation using miles. I paid the change fee instead of risking tight connection. Also if you could pack as a carry on you would have more options.

In some ways, this is a relatively minor issue, so I appreciate all who have responded.

Because I used airline points, changing my connecting flight, even at a cost of more points or dollars, is simply not an option. Again, the only option offered is a connecting flight to Amsterdam to catch another connecting flight to Berlin, which would arrive close to midnight. I am currently booked on a flight that arrives in Berlin at 11:15 am. I am not changing.

If the Delta flight arrives in Rome on time and if the passport-controls lines are reasonable, I should be able to make the connecting flight. I have been told that a checked-in suitcase is less likely to miss the connecting flight than I am. If I miss the connecting flight, then Delta without any extra costs will have to find me a later flight, which hopefully will not cost me more than a few hours. And of course, the connecting Alitalia flight might be delayed.

65 minutes to catch a connecting flight in an European airport after a flight from the US is much too short, and I knew that when I booked my flights. But I have been told reportedly the connection time is "legal," and when you use points, there are often fewer choices than you would like. There is nothing left to do except hope that the Atlanta flight arrives on time and expect to move quickly.

Richard, re the passport queues. There will be two separate queues, "EU passports" and "All other passports".
The "EU passports" is quicker, all they have to do is scan the passport to check it is genuine and check you look like your photo.
The "All other passports" is a lot slower, they ask questions, check visas if needed, stamp passports etc. I guess you will be in this queue.