No, with Uber, you have arrange on arrival, and rely on there being a car within a few minutes' of the airport (you get 15 minutes waiting time).

Looking on the app right now, I can see half a dozen UberPOP and UberX within 3 minutes of the Roissy terminals.

And yes, Paris is a pain on getting taxi pickups as the antiquated system of 'bornes de taxi' persists. This page may help if you want to use this system at any point (you basically ring up a phone on the taxi rank and the taxi will come and pick you up - meter starts then, of course).