Local tradition holds that the structure was raised on top of a rath, the Irish term for a roughly circular earthwork enclosure used as a farmstead or defended homestead during the early medieval period. That would make the site a layered one, with a medieval tower planted deliberately, or perhaps opportunistically, on an older earthwork whose origins stretch back centuries further.

The most compelling piece of evidence for this comes not from excavation but from cartography. The first edition Ordnance Survey map, surveyed in 1839, shows a roughly circular ring of trees around the castle, with a diameter of approximately thirty metres. That kind of planting often follows the line of an older earthen bank, the trees taking root along a feature that was still visible, or at least still present in the soil, at the time of mapping. The observation was recorded by O'Kelly in 1969, who noted the tradition connecting the castle to the earlier rath. Whether that tradition reflects folk memory of an actual pre-Norman enclosure, or is a later rationalisation of an unusual landscape feature, is difficult to say without further investigation.

What makes the site quietly puzzling now is the absence of that outer ring in modern satellite imagery. The trees and any trace of an enclosing element appear to have vanished entirely, leaving only the castle itself visible from above. The landscape has effectively erased the clue that the 1839 map preserved, so the question of whether a rath truly underlies Drumroe Castle may remain open unless the ground itself is one day examined more closely.