I read a number of horror stories about returning rental cars to CDG. We had one for our 8 day trip which ended this morning (January 1st 2019) as we traveled to various Schengen locations. I was stressed to read how many people had trouble with returns to Terminal 2 (2F in my case)
The biggest factor was not having an actual pin point address for the return. However, that turns out not to be that much of a factor if you read the signs. They are clearly labeled Voitures de Location with Car Rental underneath that as well as the corresponding terminal locations. You basically keep to the left when following the signs.
I did this very early in the morning during darkness and found all my worry was for nothing, much to my wife's chagrin. We ended up being a bit earlier than we needed to be but being new year's day, with all the protests and higher security levels, I'm not regretting sitting here at the gate writing this up.
Just remember to read the signs, stay left while following them, slow down, and you will make it there just fine. Give yourself the appropriate amount of time as well and you'll be just fine.