Bertha was born in April 1890 to parents John and Emma Roberts. Her father worked as a general labourer. Bertha had four older sisters (Elizabeth, Susanna, Mary and Hannah) and two brothers (George and Thomas).
By the 1911 census Bertha was working for William and Savinia Ridley Thomas at Rose Hill in Whittington as a domestic servant. In 1912 she married Thomas E Roberts.