For those that may offer additional input, the following information may be helpful:
Columbia County, AR marriage records
William G. Berry, age 27 resident of Columbia County married to Senthey Roberts age 24 resident of Columbia County on 8 Nov 1854.
This couple is shown on the 1860 census in Angelina County, TX. In the same township is a Phil(ander?) Berry born c1820 in Mississippi. Perhaps he was a relative, though I did not find him earlier or later than that census listing. If he lived long enough, his death certificate would possibly give the names of parents.
I did not see any obvious match to Cynthia on the 1850 in either Arkansas or Louisiana, but do notice this one in Lafayette County adjacent to Columbia:
Lafayette County, AR
Red River Township, family 33/33
David H. Dickson, 33, farmer, $6000, LA
James R. Roberts, 41, overseer, VA
Cinthia ", 18, LA
William C. ", 13, TN
Lucy A. ", 11, TN
I would be interested in seeing if this Cynthia is the wife or daughter-in-law of this James Roberts. A check of that county's deeds or probate records may be helpful. Nearby counties in Arkansas and parishes in Louisiana could be checked for a marriage record as well.
As Welsh (Welch) is not a very common name, it may be worthwhile to check north Louisiana parish probate and deed records to see if you can find the father. Start with the 1830 and 1840 censuses as Cynthia's father, in theory, would be listed. See if you can track each of those men and identify a place of death where estate records may be filed. The LDS church has digitized some of these parish records. Though they are not computer indexed, browse to each record and look in the front of the volume for the clerk's index. Here's a link:https://familysearch.org/search/image/index#uri=https://fami...
Since William Berry was in Columbia County in 1854, I would suggest checking that county's tax and deed records to see what turns up. As families tended to travel together, perhaps there are other relatives that you can find to help you back into his parentage. He should have been easy to find on the 1850, but I turned up nothing.
William is shown with daughter Mary Robertson in Hamilton County, TX in 1900. I note that William's parents are listed as born in Ireland, so that may be useful down the road.
Hope this helps,