He was called 'Big Jim' and 'the uncrowned King of New Zealand' in recognition of the considerable influence he wielded during the period of the First Labour Government over policy creation and implementation.

Lucy became deaf during her third pregnancy and later developed rheumatoid arthritis leaving her largely handicapped.

[2] Roberts became one of the dominant figures of the Labour Party, serving as vice-president from 1934 to 1936, and national president between 1937 and 1950.

[2] Roberts sought the nomination for the Wellington West electorate ahead of the 1938 general election, but was unsuccessful.

Roberts was appointed a Companion of the Order of St Michael and St George in the 1958 Queen's Birthday Honours, in recognition of his services as secretary of the New Zealand Waterside Workers' Federation and the Alliance of Labour.