This is a classic example of several people with the same name being born in the same area in the same year!
You can see that Edward PRICHARD is not a part of the ROBERTS family by the way the census is marked in 1841. He is a separate person within the same household.
Yes, that plus the fact that he's not listed sequentially, by age, suggests he's not a child of the family.
You have access to Welsh records on FamilySearch
You first need to have a look at Edward's marriage record to see who his father was and his father's occupation.
According to his 1861 marriage certificate, his father
was John Roberts (labourer) but that's not necessarily so. It looks as if he'd been fully accepted as the son of John & Catherine, as evidenced by the 1851 and 1861 censuses.
Two Edwards, one the son of Zachariah PRITCHARD and Jane and the other the son of James PRITCHARD and Margaret (both mothers were maiden surname WILLIAMS) - both of those boys appear to be with their own families in further census records.
Either one of these Edwards would have been a likely candidate, but for the fact that they are 'with their own families in further census records'. Blast!
Maybe you will need to follow all of the Edwards baptised to see if they appear in 1841/51.
It looks like that's what I'll have to do! Thank you all for your help.