I'm looking for my Granmother, her name was Margaret Ellen Williams (Maggie) she was born 28th April 1905 and died 7th Feb 1984, she was married to a man called Owen John Roberts
Hello and welcome to Rootschat
When and where did they marry?
Do you have the marriage certificate? If not, obtaining this would confirm her father's name and occupation, witnesses maybe family members
Edit to add
Possible marriage entry on FreeBMD
Sep 1932 St. Asaph 11b 572
Roberts Owen J Williams
Williams Margaret E Roberts
and on North Wales BMD
1932 St Asaph, Civil Marriage
ROBERTS Owen John
WILLIAMS Margaret Ellen
Would agree with Ladyhawk, her marriage details would confirm or rule out if her father was William. His occupation could have changed post 1911 to their marriage date. Unable to see father's occupation in 1921.
There was a number of children who died, but all boys on census except Maggie Ellen so there seems a lot of similarity to your family info.
Welsh family history can be difficult, certs are needed to confirm you are on correct family path.
This is very likely her birth registration, which would give parents and date of birth. PDF on GRO is around £7.00
WILLIAMS, MARGARET ELLEN mother's maiden name WILLIAMS
GRO Reference: 1905 J Quarter in BANGOR Volume 11B Page 465
Let us know if you obtain any certificates
Good Luck
Cas