George Roberts was born in 1857 and I presume it is G Roberts, ships officer (2nd Mate), 51 Bede St, Tyne Docks, South Shields (Released 21/12/1915) that you are interested in.
He was aboard the steamship FLEETWING, official number, 125421, detained 4 August 1914.
G. G. Roberts, of Holyhead, was named in a list of merchant seamen interned at Ruhleben, as published by the Scotsman newspaper on 7/1/1915 (p.7).
This was 2nd Mate, G.G. Roberts who was aboard CITY OF CADIZ, official number, 45019. Steamship detained 4 August 1914. I believe this is not the man the op is searching for.
Regards
Hugh