Archaeologists employed by South East Water made the finds ahead of a £321,000 scheme to lay a pipe near Bearsted.
Tim Allen, from Kent Archaeological Projects, described the discoveries as “very exciting”.
South East Water said it had the survey carried out as a precaution.
Mr Allen said: “We are very excited as we have found evidence not only of a manor house dating back to early medieval times, but also as we investigated further we discovered a Roman road which was not known about before.
“We are grateful to South East Water for their consistently responsible and serious approach towards our archaeological heritage and their efforts to advance our knowledge of the history of the county.”
Paul Clifford, of South East Water, said “This exciting find, on private land near Bearsted, has emerged during careful archaeological surveys carried out during the excavation work before we lay the pipe.
“On schemes such as this we take the extra precaution of having archaeologists working alongside our contractors to ensure that if we do find anything of historical significance, then we can halt work for further investigations.
“That ensures we can continue to protect and record our ancient heritage.”
Source: BBC News