Usually airlines book the hotel themselves as they have contracts with a list of hotels with rather cheap prices.
Unless there is a conundrum (like many flight delays due to all kinds of reasons), airlines would provide you with a hotel (that might differ by class of service) and would not refund you if you decline it and book your own hotel. A best, you would get some amount (like what they would have paid) but this is a long process if successful..
All hotels near CDG are decent. Sheraton makes you pay the convenience that it is within the terminal rather than having t take a shuttle.