Does anyone know what are the openning hours of the RER ticket office (called: Billets Ile-de-France) in CDG airport in Paris?
My flight arrives at 05:45AM, and I'd like to buy the "Pass - Navigo Découverte" ticket that serves for 1 week, and I don't know how long will I have to wait for the office to open.
Thanks in advance.

From the Transilien website:

AEROPORT CHARLES DE GAULLE 2 TGV
Présence commerciale en gare : Tous les jours de 05h50 à 00h30

If you are arriving at terminal 1:

AEROPORT CHARLES DE GAULLE 1
Présence commerciale en gare : Tous les jours de 05h50 à 01h00

I/m not sure that it means that the tickets' office is open as well at this hour.

I would be pretty sure you won't get to the ticket windown until 6:30 or so anyway. I would not imagine the station would be open without it being "manned". Do you have an appointment you have to get to in Paris?

Which zones are you getting the Navigo Decouverte for? If it's just for zones 1-2, get it in Paris; just carry enough coins to buy one RER ticket from the machines for Roissy to Paris.

are not there automatic ticket machines that at least some American credit cards can use to buy these type tickets?

Présence commerciale en gare means exactly that - they're open!

Anyway, Mademoiselle is correct - you don't even need to buy the pass at that point. All you need is to get yourself into Paris.

Yes, that is when the ticket window opens. "Commercial presence" means selling things.

I'd like to buy the pass for zones 1-5, so as to use it for the train to Paris. The machines do not have the Navigo Découverte. I hope the office is open when I get there.
Thanks to all for the info.

Are you re-filling your current Navigo card? If so you can do that via a machine but like said above you'll need to have € change unless you have a credit card that would work.

I knew it was open by 6 because that's when we bought tickets in March. Only one clerk, but she was not overworked at that hour.