A victualler sells alcohol usually in an inn, they would be licensed. It is still a term used today.
No they lived in the Parish of All Saints, that's a district, of Canterbury I think.
I have looked for William marrying as William Christmas Roberts or William C Roberts from 1901 back to 1891 and there is no entry, therefore, if he married, he married as William Roberts, which is a really common name, it would need a close look at every William Roberts entry for any clue in the registration district to spot a likelt choice. Or , a search from 1901 forwards in the index to spot any Roberts children being registered at Hornsey maybe, or whichever registration district that was, I have checked ther 1911 free search for a william and sarah toberts and there asre a couple but it costs to look at the original entry. you would need to do that to eliminate the wrong ones.