Chasing "Roberts" in North Wales is daunting at the best of times. In addition the name "Mandle" is as rare as hens' teeth.
FindMyPast Baptisms -
1. Image/Transcript
13 Mar 1834, Sarah Ann dau of Robert and Ann Roberts, abode Gwern Glefryd, occpn. bricklayer
2. Transcript only
Sarah Ann Roberts, 13 Mar 1836**, place St Asaph, parents Robert and Ann Roberts
3. Image/Transcript
19 July 1844, Susannah daughter of Robert & Ann Roberts, abode Penyllan Brynpolyn, occpn bricklayer, place of baptism St. Asaph
As mentioned no Susannah with mother's maiden name Mandle (or similar) to be found on GRO. There are Susannah's that "fit" but not a "Mandle"
I've been chasing the 1834 baptism re. Sarah Ann in 1841.
** - as transcribed