There are fast direct trains from Kaiserslautern to Paris, where you would change to local transport (depending on which Paris airport, as there is more than one). Check www.bahn.com for schedules and prices.
However, the fast trains run quite infrequently; so in the (unlikely, but not impossible) case that a train is cancelled, you cannot just take the next one an hour later. I would therefore leave a generous buffer if it is an international flight; maybe plan some sightseeing in Paris while leaving your luggage at the station.
Edited to add: And yes, of course it is straightforward. Unfortunately, the French insist that you need a seat reservation on a TGV train (and, in French stations, they want you to be at the platform more than 2 minutes before departure, which can be surprising if you are not used to that); but other than that, it is just a normal train journey.Edited: 16 March 2018, 15:52
It will probably be best to get from CDG to the train station and then take the next available train. What is the travel time difference between "fast" and regular train service?
Fast: 2 hours 40 minutes. Other connections: 4 to 5 hours. As said, check out the connections on bahn.com
There is nothing wrong with going directly to the airport, but I would definitely factor in possible train delays
Edit: I have just seen that in your post, you ask for the connection from Paris, whereas the title is about transport to Paris. Accounting for delays makes sense in both cases, but missing a train is probably less bad than missing an international flight :-)Edited: 17 March 2018, 17:49
If your trip is still in the future, please be aware of strikes of French railway workers on several days between Apr 3 and Jun 28. For latest information, please check www.cestlagreve.fr/greve/sncf-avril-2018/ or https://www.oui.sncf/train/greve (French language only, but google translate should help you).