Roissy / Charles De Gaulle: the ROISSYBUS leaves every 15mn from
Door 10 Hall A or Door 12 Hall D and drops you "Rue Scribe" (see
area map),
near "Place de l'Opera" (45mn, 48FF/person).
There you have a 15mn walk to place St Augustin or you can take the
métro.
The best is probably to walk to "Havre-Caumartin" and then to take the line 9 direction
"Pont de Sèvres" (only one station to "Saint Augustin").
Other means from Roissy to Paris
(Other busses, train, ...)