Is there a shuttle in Paris (like I found in Amsterdam) that picks you up at the hotel and brings you to the airport?
Taxis do a good job. 50 EUR from the Right Bank and 55 EUR from the Left Bank, plus a nominal dispatch fee. Have your hotel order it for you.
Your hotel may be able to schedule a shuttle for you, ask them when you check in. If I remember correctly, in 2015 it was about €26 from the Rue Cler area to CDG.
I suspect the shuttle fee of 26 euro is per person, in which case, unless you are travelling alone, a taxi is better and cheaper.
If you are near the Montparnasse train station, there is a regular bus shuttle to CDG . I took it in May, and it was great. It was around $30, but you have to pay in euros or with a credit card. I believe there are other similar shuttles in and around Paris. Check the Internet. There are also shuttles that pick you up at your hotel. You have to reserve it the night before with the concierge.
Our Paris hotel (with our RS tour) arranged for transport to the airport. It worked very well, easy way to get to the airport, can’t remember the price, but felt it was well worth it at the time as we had an early morning flight.