How do they know it’s Roman?................
Because they are known to have been Roman all over the Europe at that time.
“How do they know it’s Roman?................”
This:
“...part of the ancient settlement of Maestriana...”
“Maestriana was an ancient Roman settlement located beneath modern-day Zalaszentgrót, Hungary, known for its strategic importance as a waystation on the Roman frontier in the province of Pannonia.”