The dedication alone is unusual. Ireland has no shortage of early medieval saints whose cults survived only in the names of wells, churches, and parishes long after any written record of their lives had dissolved, and Saint Marcan appears to belong firmly to that category, a local holy person whose memory clung to this particular patch of ground while the details faded.

Beyond the name and the location, the documentary record for this site is presently thin. What can be said is that ruined churches of this kind in the west of Ireland typically have their origins in the early Christian period, sometimes built on or near sites of even older significance, and that many were maintained as places of burial and local devotion well into the post-medieval centuries. The fabric of such buildings often tells a layered story, with stonework from different periods patched together, and small details like cut-stone door jambs or fragments of Romanesque ornament occasionally surviving in the rubble. Whether any such features remain at Rosclave is not currently documented in available sources.

The site sits in a part of Mayo where early ecclesiastical remains are not uncommon, a county that preserves traces of the intense monastic and parish activity of the early and medieval church across its bogs, headlands, and islands. Saint Marcan's, wherever exactly its walls now stand, is one small piece of that longer story, waiting for fuller attention.