From ROUBAIX Birth/Marriage indexes (Tables Decennales)
Marriage : Alphonse Joseph CARBON/Augustine Sophie Honore DAVRAIN 24 May 1869
Birth: Henri Auguste CARBON April 1886 (looks like the 7th).
The only other Henri CARBON born in the Roubaix indexes between 1883-92 was in 1892 – so probably not the right one.
You can get the certificates here – they should be free. Makes sure you choose the ‘acte avec filiation’ option.http://www.ville-roubaix.fr/demarche-en-ligne-etat-civil.html
Edit: I forgot to mention that the parents names/adresses,professions, date of marriage, as well as lots information will be on their marriage certificate - French certificates are much more informative than British ones so perhaps what you saw was not an 'acte avec filiation' (which mentions parents)