Ali,
As you obviously know, if William Ramsey was a farm labourer that will make him harder to trace. Labourers often moved around a lot (to follow the available wiork) and so can be very elusive. Moving around may explain the apparent confusion between Donegal and Derry. The answer might be that the family lived in both over the years.
Knowing that William was a labourer probably rules out the two in the Donegal tithe applotment records as they would have been farmers.
The term Protestant includes a wide variety of denominations, not just Church of Ireland. The most common in that general area would be Presbyterian (mostly descendants of Scots who moved to the area in the 1600s) but includes Methodist, Baptist, Reformed Presbyterians and so on. Do you know what church they used in Scotland? Was it Church of Scotland? If so, that points to them being Presbyterian.
If you can narrow the deno0mination down you could try searching the surviving records for the area. Many of them are not on-line and it would involve you or a researcher going through them in PRONI. William & Rose must have been born in 1790 or earlier and not all churches have records that far back but you might get lucky. But it would be a bit of a needle in a haystack.
Death registration only started in Ireland in 1864. I searched the records for Rose Ramsey/Ramsay died 1864 – 1869 but there were none, so that suggests she died before 1864. There are a lot of William R deaths in the same period. If you narrow them by location and likely age there are 5 or 6. Those records are not on-line free though and are pay to view. But if he too died pre 1864 then there's probably no record. Also if he was a labourer, then the family probably wouldn’t be able to afford a gravestone so they may be in unmarked graves.
The 1831 census of Co. Derry has survived. There was just 1 William Ramsay in it. He lived alone in Kildoag, and was Church of Ireland:
http://www.census.nationalarchives.ie/pages/1831/Londonderry/Tirkeeran/Tirkeran/Kildoag/6/
Kildoag is in the parish of Cumber Lower, just outside the city of Londonderry. Cumber Lower’s baptisms start in 1804, marriages in 1806. Copy in PRONI plus some years are on rootsireland (subscription). Might be worth checking. Kildoag is/was a largely agricultural area. In the 1831 census there were 22 households in it.
The 1831 census for Donegal has not survived.
Possibly DNA testing may be a way of matching with others who have additional information about where the family originate. Family Tree DNA reportedly has more people with Ulster roots than any other company. That obviously increases the chances of finding a match. You might want to try them or, if you have already tested, you can transfer your results to them for no fee.
The North of Ireland Family History Society is running an Ulster DNA project in conjunction with FTDNA and can offer testing kits at a reduced price. http://www.nifhs.org (Go to DNA project on the website).
