I am having difficulty finding online updated rates for the Roissy Bus from CDG to Opera Garnier. I am hoping recent travelers can advise. Also is there a round trip rate that is a better deal than two one-way tickets? Do we purchase the tickets on the bus at CDG, or is there a kiosk?

You can find it on the transportation website:
www.ratp.fr
It should still be about 8E and there is no break for r/t. Buy it from the driver.

Thank you, Travelnut, for the Roissy Bus information. When we get off at Opera Garnier, can you please advise where we might find a taxi stand for a taxi to our hotel?

Take the metro from Opera to your hotel, it will save you money. I bet there is a metro station close to your hotel.

According to my notes (I haven't done this yet), the Roissybus (€8.50, by the way) stops on Rue Scribe, and there are taxis at the Hotel Intercontinental across the street. If you follow this link (http://tinyurl.com/hy9wv) and click on the little map symbol beside Paris - Opera, you can also see the nearby bus stops and metro stations.

There are machines at the airport, but my experience was that they needed credit cards with the smart chip.

If you choose to, there is a Metro station nearby.

Also, in case you did not know , there are also Air France buses that go to central Paris from CDG.