Earlier than Roman.
Many archeologists believe that Stonehenge is a temple to the sun god, as described by the classical historian Diodorus Siculus who cites the fourth century BC GREEK geographer, Hecataeus of Abdera, in a key 1st century classical source.
AND here is the legend:
A classical legend associated with the Greek Oracle of Delphi is related to Stonehenge’s past. It states that the oracle at Delphi functioned for only part of the year because, for three months around the winter solstice, the site’s sun god Apollo) went to the “land of the hyperboreans” (literally “the land of the people beyond the north wind!”), which is generally believed to be Britain.
Significantly, Stonehenge is aligned with the winter as well as the summer solstice.
The Greeks knew about this place long before the Romans ever got there.
“The Greeks knew about this place long before the Romans ever got there.”
And probably the Phoenicians before the Greeks.
It was not unusual for the Romans to worship local Gods and incorporate them into their Pantheon. Pagans were much more ecumenical than Judaeo-Christians. Aquae Sulis
is an example of Romans incorporating a local deity into their Pantheon by identifying her with a Roman goddess.
The Monolith builders antedated the Romans, Greeks, Phoenicians and Celts.