You just turned off data roaming, that means you can’t use data but your phone would still be able to be used for calls and texts which is why you see the R and why you received the notice the other day.
As long as you don’t send a text, or spend any time on the phone in a call you shouldn’t see any roaming charges though.
So just to be clear, the phone still roams on various networks so it can receive calls and texts but as long as I don't answer any calls or send any texts (I can still read the ones sent to me), I won't incur roaming charges?
As an aside I received a notification today that I was roaming on a network from France although I have been in Germany all day.
Correct.
And were you near the Germany and France boarder?
If so it likely connect to the stronger french cell tower