I noted a TGV station on the CDG Terminal 2 map. Will it be possible for me to take a train from Aix en Provence directly to CDG in order to catch my flight to Denver?
Yes. It depends on the day and time of course; some are direct or have a connection
Do your schedule search to Aeroport Charles de Gaulle TGV station, or some variation on that station name, rather than to Paris, for the best shot at the results you want. View details to see any connection points. The direct trains take 4 hours and run a few times per day from Aix en Provence TGV station.
Looking Up Train Schedules and Routes Online gives you the Deutsche Bahn train schedule link and tips for using it. This one doesn't sell tickets; they're available at www.oui.sncf, trainline.eu, and this site.