Hi folks,
Sorry to jump in but I have been to the Roman site at Tomen-y-Mur and (as far as I can remember) doesn't match the description given by Sanctuary. The site is clearly Roman - it even has a reconstructed section of fort wall - very impressive it is too!
I have checked my O/S map and can't see any cairns / barrows near by either so I guess Sanctuary was looking elsewhere?
Hope this helps?