I looked for Mary Roberts in 1841 and still in Raven Street. This gave information which led to the childrens' baptisms and marriage of parents which, unusually, gave their parents:-
1841 Raven Street, Welshpool
William Roberts 50 1791 Joiner b Montgomeryshire
Ann Roberts 50 1791 b Montgomeryshire
William Roberts 20 1821 Mason b Montgomeryshire
Ann Roberts 25 1816 b b Montgomeryshire
Thomas Roberts 15 1826 b Montgomeryshire
John Roberts 10 1831 b Montgomeryshire
Margaret Griffiths 20 1821 Soldier's Wife b Montgomeryshire
William Roberts, age 22, son of Owen and Jane Roberts, married Ann Waring, age 21, daughter of Thomas and Elizabeth Waring of this Parish, on 17th July 1810
Elizabeth Roberts, daughter of William and Ann of Welshpool, baptised on 25th Feb 1816
Joseph Roberts, son of William, a joiner, and Ann of Pooltown, baptised on 30th May 1813
Margaret Roberts, daughter of William, a joiner, and Ann of Pooltown, baptised on 25th Feb 1816
William Roberts, son of William, a joiner, and Ann of Pooltown, baptised on 14th June 1818
Ann Phalia/Thalia Roberts, daughter of William, a joiner, and Ann of Pooltown, babtised on 11th June 1820
Thomas Roberts, son of William, a joiner, and Ann of Pooltown, baptised on 25th May 1823
John Roberts, son of William, a joiner, and Ann of Pooltown, baptised on 22nd May 1831
George Roberts, son of William, a joiner, and Ann of Pooltown, baptised on 3rd June 1834
Ann Waring
Daughter of Thomas and Elizabeth (Davies, married 2 Oct 1775 in Welshpool)
Born: 29 Sep 1788
Baptised: 31 Oct 1788 in Welshpool
Trees for brother, Edward, but inactive:
https://www.ancestry.co.uk/family-tree/tree/70538537/family?cfpid=392355375220https://www.ancestry.co.uk/family-tree/tree/88059678/family?cfpid=46567216410William Roberts
son of Owen and Jane (Probably Williams, married 17 Jun 177 at Llanfihangel-Yng-Ngwynfa, Owen of Llanfyllin)
Born: 5 Nov 1788
Baptised: 7 Nov 1788 in Llanfyllin
David