We will soon be flying from Los Angeles on Air France to Rome via Charles de Gaulle. (I am not sure whether we will need to change terminals.) Will we need to go through passport control in Paris?
Yes, immigration in Paris. Customs in Rome.
Even if you are just moving from Terminal 2E to 2F, as I have done coming from Seattle, it's a fair distance. You should be able to see the terminal information in your online flight details. You will probably need all the time allotted, so don't dawdle. If there's a significant delay, then of course Air France would be responsible to put you on a later connection to Rome.