I think I read an article a while back that said they found evidence of a Roman fort in Ireland
Some archaeologists have suggested the fort was a bridgehead for Roman military campaigns, while others suggest it was a Roman trading colony, or at least the site of a regular trading "fair", or a native Irish settlement that traded with Roman Britain.
The site was acquired, reportedly for about €1 million, by Fingal County Council in 2017. In early 2018 they announced a Draft Conservation and Management Plan for consultation, including protection from further damage by motorbike scrambling, and integration into coastal walking paths. The purchase has raised hopes that the site will finally receive proper archaeological investigation, which will answer many of the questions that have been the subject of speculation for decades.
Drumanagh - Wikipedia
Interesting article on Drumanagh and the question of whether the Romans invaded Ireland or not:
Roman contacts with Ireland | Irish Archaeology
« The question of whether the Romans invaded Ireland remains unanswered, although the current archaeological evidence would suggest that there were no large scale military incursions. For example, sites normally associated with the Roman military in Britain, such as large square/rectangular forts and linear, well-made roads, are conspicuously absent from the Irish archaeological record. It does seem, however, that there were extensive trade contacts between Ireland and Britain and it is likely that Romanised Britons and indeed Romans themselves would have been regular visitors to Irish shores. They probably came to trade, make political alliances, and to visit sacred sites such as Newgrange. Some may even have stayed long enough to form small communities, who chose to bury their dead according to Roman custom. »