[2][3] Roberts served as NASA's first Flight Dynamics Officer with Project Mercury that put the first American into space.

The family settled on Anglesey and the records show that he successfully sat his Scholarship Exam in Ysgol Parc y Bont, Llanddaniel Fab in July 1938.

[6] After leaving Beaumaris Grammar School, he began an engineering apprenticeship with the aero- and marine-engineering company Saunders-Roe at Fryars Bay, Llanfaes, Anglesey, some eight miles from Llanddaniel Fab.

[12] When the Avro Arrow project was suddenly cancelled by the Canadian government on 20 February 1959, many Avro Canada engineers including Roberts followed the lead of Jim Chamberlin and moved to the United States to join NASA's Space Task Group at Langley Research Center in Hampton, Virginia.

In 1959, Gilruth's group was greatly expanded by the addition of the engineers from Canada who had been left without jobs when the Avro Arrow project was cancelled.

[4] Roberts may have popularised the use of the phrase "A-OK", making those three letters a universal symbol meaning "in perfect working order.

"[dubious – discuss][4] The first documented use of the English language phrase "A-OK" is contained within a memo from Tecwyn Roberts, Flight Dynamics Officer, to Flight Director (entitled "Report on Test 3805", dated 2 February 1961) in penciled notes on the countdown of MR-2, dated 31 January 1961.

U.S. Air Force Lt. Col. John "Shorty" Powers popularised the expression while NASA's public affairs officer for Project Mercury.

Roberts was present when the Honeysuckle Creek Tracking Station was opened by Australian Prime Minister Harold Holt on 17 March 1967.

[2] In 1972,[18] Roberts became Director of Networks at the Goddard Space Flight Center,[24] a position he still held by the time of the Apollo–Soyuz Test Project in July 1975.

[24] In 1979, Roberts retired as Director of Networks at Goddard and from NASA and became a consultant to the Bendix Field Engineering Corporation.