How to get on Roissybus from Charles de Gaulle airport terminal 2E to Paris-Opéra 
https://youtu.be/SqRZhGvd780

Roissybus provides non-stop services between Charles de Gaulle airport and the Paris-Opéra. The ticket machines at the departure points at RATP counters in terminals. It takes for 60 minutes, depending on traffic.
Gate transit connecting train at CDG Terminal 2E hall M, L, K, you will take a connection train to your first stop to passport control/immigration at “2E – hall K” when you are arriving at terminal 2E such as Air France.

Departure Times from Paris to CDG:
The bus departs from the Rue Scribe/Opera Garnier stop starting at 5:15 am, with buses every 15 minutes until 8:00 pm. Between 8:00 pm to 10:00 pm, departures are every 20 minutes; from 10:00 pm to 12:30 am, service slows to 30-minute intervals. The journey takes about 60 to 75 minutes, depending on traffic conditions.

Departure Times from CDG to Paris :
From CDG, the Roissybus departs daily from 6:00 am to 8:45, leaving at 15 minute intervals, and between 8:45 pm to 12:30 am, every 20 minutes.

Buying Tickets and Current Fares
There are several ways to purchase tickets (one-way or round-trip fares). You can buy them directly on the bus, but do keep in mind that you’ll need to pay in cash; debit and credit cards are not accepted onboard. Tickets are also available for sale at any Paris Metro (RATP) station in the city, and at RATP counters at CDG Airport (terminals 1, 2B, and 2D). The ticket offices at the airport are open from 7:30 a.m. to 6:30 p.m.
If you already have a “Paris Visite” metro ticket that covers zones 1-5, the ticket may be used for a Roissybus trip. Navigo transport passes may also be used.