You will probably have found these:-
1901 Census, Robert Roberts, Tynyfawnog & Margaret, born 1847 in Melin y Coed Denbighshire are on RG 13/5246 page 5 with daughter Jennie, born in Llangwm in 1885.
In 1911 they are at the same address with Margaret from Llanrwst(not far away) and adopted son Robert Edward Rowlands aged 8, born in the Parish of Llangwm.
That will. narrow things down a bit.
The Burial indices from the Clwyd Family History Soc are available for Capel y Groes & Gellioedd , Ind) (not in NLW) in the Parish of Llangwm, otherwise Capel Dinmael & Cefn (Dinmael has a Cemetery, I've been there), or Ty Nant (Wes) (

Cemetery) or Llangwm Parish Church will need to be visited
Why don't you post a Note on the Denbighshire Rootschat site. Someone may have some info on Robert Roberts, Tynyfawnog. Loads of people have unofficial lists of Memorial Inscriptions.
Regards
Alwyn