I understand there are rest stops on the toll highways but are there any on the non toll highways as well?
We stopped at one on the N10 between Angoulême and Poitiers last month. There were picnic tables, a lady with a type of food truck with coffee, soft drinks and snacks.. Also some rustic public toilets.
Yes there are also rest areas on the free highways and also gas stations (generally with a rest area).
There may also sometimes be rest areas on the main national roads (RN)
This sign indicates a rest area (without gas station) 300 meters away. The next one is 17km away
https://static.wikia.nocookie.net/routes/images/a/a8/P1200822.jpg/revision/latest?cb=20120315201659
This one a rest area on a national road:
And if you see this sign (on national roads)
https://upload.wikimedia.org/wikipedia/commons/9/93/Logo_Routier_Rond.jpg
It's a "Routier" restaurant (for truckers) which have a good reputation, not expensive, traditional full meal at less than 15€, good atmosphere.
Watch for a sign on the right side of the road, with an image of a picnic table, and a pine tree bending towards the table. That doesn’t mean there will be shade, though, or other facilities.
Anyone know of any rest stops between CDG and Fontainebleau?
Get yourself a decent navigation app based on open street maps (ie, not Google), zoom in on the area you wish to search, and search "picnic". It will show you where the picnic tables/picnic areas are. Or, search "aire" and it will show you where the rest areas are.
Armed with that information, go to streetview and have a look to see what facilities are at each place.
Some will have toilets, tables and shade, some will just be a slightly off road parking area.
There are areas on most main roads - Autoroutes definitively, most Routes Nationale, and many departmental roads. It's just a matter of luck if you can find one when you decide you need one.
The few I saw reminded me of ones seen in the states in the 1960s; picnic tables and maybe a few trees. They were nothing like the ones on turnpikes or interstates.
Regarding the French highways (and only the highways):
All the services available for the northern part: (zoom to see the details of a specific area)
https://www.sanef.com/en/my-journey/real-time-traffic
The same for the southern part: (in French only, use an online translator)
https://www.vinci-autoroutes.com/fr/mon-trajet/?area=repos&area=service&filter-status=1
On the right, tick the box(es) corresponding to the service(s) to be displayed