Hello Steve,
This is the first chance I have had to reply to your query. I wouldn't like to say whether there could have been more than one Thomas Rogers in Llansilin. For total accuracy, I would assume that there could be more than one and aim to identify "your" Thomas if possible.
More often than not, it is impossible to be 100% certain in these cases. My 4xgt grandmother was Mary Williams born c1790 in Ysceifiog. When I looked at the Parish Registers there were 4 people with the name of Mary Williams baptised there around then. No way of ever knowing which one it was.
I suspect that people didn't know their exact date of birth accurately in those days. I have found many instances where ages have been recorded at death incorrectly. Also, on the census returns where ages seem to vary with each one. May be people didn't know the dates well, no calendars etc then.
You may be luckier, see what Gadget can find.
Jo