+1 for IGN maps, you can even buy 1:25000 maps if you fancy that level of details, but in my view, their 1:100000 maps are better suited for cycling purpose.
Beware of the fact that you cannot always rely on road numbering for guessing whether a road is cyclable or not. N roads used to be main roads with heavy traffic, while D roads used to be secondary and quieter roads. This is not true anymore, some former N roads have been relabelled D. A quick glance on Google StreetView is now the only way to be sure!