British civil engineer who pioneered new design and construction methods in a series of major bridges including the 3,300-foot (1,006-metre) Firth of Forth highway bridge in Scotland, the seventh longest in the world.

After attending City and Guilds College of the University of London (B.S., 1923), he became a civil engineer and worked on the Sydney Harbour Bridge and on the Otto Beit suspension bridge across the Zambezi in what was then Southern Rhodesia. A brilliant designer, he adopted new welding methods and the use of high-tensile steel and introduced box columns and girders in the construction of power stations, thereby using less steel. Roberts's designs, which called for lighter construction, better stability, and lower cost, were implemented in such engineering masterpieces as the Severn River Bridge in western England, the Auckland Harbour Bridge in New Zealand, the Volta Bridge in Ghana, and the suspension bridge across the Bosporus in Turkey.

Roberts also developed all-welded ships in World War II and designed the Dome of Discovery for the Festival of Britain in 1951, the Babcock 500-ton Goliath crane, and a 210-ft- (64-m-) diameter radio telescope in Australia.

In 1965 (upon completion of the Firth of Forth bridge) he was knighted and elected a fellow of the Royal Society.