Hello there,
Rosières-en-Santerre is in the departement of Somme (80), whose archives are now available on-line on their website:
http://archives.somme.fr/Specifically, the "État-civil" encompasses the parish registers (before 1792) and civil registry (after 1792) :
http://archives.somme.fr/?id=recherche_guidee_etat_civilA short guide in english (pdf file):
http://archives.somme.fr/download.cgi?filename=accounts/mnes...The oldest parish register available for Rosières is given for 1679, but if you look at the records, the first certificate is dated 1642... it's in poor state and probably incomplete though...
---> Rosières-En-Santerre : Baptêmes, Mariages, Sépultures (1679-1699)
Ref : 1MI_EC_177
Direct link:
http://archives.somme.fr/ark:/58483/a011261413225inBcvS/1/1To go further, you'll probably need to use other types of archives such as notarial archives, but I don't know if they still exist and even so, you'd need someone on the premises to search them anyway.
You'll find other researchers studying this family on geneanet.org but they don't have more informations than you. One exception though, John BLANCHETTE (
http://gw0.geneanet.org/index.php3?b=dblanchette&lang=en...) who gives Pierre BLANCHET as Noël BLANCHET's father. You might want to ask his sources?
Good luck!
Amandine