Is it Hannah’s maiden name you are looking for? Not quite sure but I can see that some children with the same names and similar dates as your 41, 51, and 61 censuses show a mother named Davies or Owen in the GRO birth records. If you look at your family as a whole only Owen is consistent as the mmn for
all the children for Richard and Hannah.
Richard Roberts baptised 5 July 1835. Son of Richard Roberts, a copperman and Hannah, abode Morriston [OPR]
Ann Roberts 1838 Swansea 1Q 26 /404 mmn OWEN
Hannah Roberts 1840 Swansea 1Q 26 / 455 mmn OWEN
Samuel Roberts 1843 Swansea 1Q 26 / 455 mmn OWEN (455 not a typo)
John Roberts 1845 Swansea 2Q 26 / 500 mmn OWEN *
Sarah Roberts 1848 Swansea 2Q 26 /585 mmn OWEN
Henry Roberts 1851 Swansea 3Q 26 /557 mmn OWEN
John Roberts 1855 Swansea 1Q 11a / 467 mmn OWEN
* Possible burial for John born 1845 – 19th April 1854 aged 9yrs, residence: Morriston, buried Llangyfelach, Saints David & Cyfelach
Marriage; Banns posted 13, 20 and 27 October 1833. Married November 2nd. Richard Robert and Hannah Owens, both of Morriston, married at Llangyfelach
https://www.familysearch.org/ark:/61903/1:1:KCYG-9QJhave asked the moderator to move this to the Glamorganshire Board, you may get more help there