On 28 August 1708 he was appointed, by royal warrant, as assistant engineer to his father at Portsmouth, and was employed on works for protecting the shore near the Blockhouse, from the sea.

At the end of July 1719, he joined the expedition to Vigo, Spain, under Richard Temple, 1st Viscount Cobham, and took part in the capture of the citadel, which surrendered on 10 October.

In Scotland he had under his charge the erection of barracks in the Highlands, as proposed by Field Marshal George Wade, at Inversnaid, Ruthven, Bernera, and Killiwhimen (Fort Augustus).

On 24 September 1722, he was promoted to engineer-in-ordinary, and on 30 October he went to the office of the Board of Ordnance in London, whence he carried out the administration of the Scottish and northern engineer districts for many years.

Among drawings by John Lambertus Romer, now held by the British Museum, are plans of Fort Augustus, Scotland, and the fortifications of Portsmouth in 1725.