Caleb Williamson (1828‒1905) was Roberts’ future father-in-law. He migrated to Melbourne during the early stages of the Victorian gold rush. He soon established prosperous mixed businesses at 181 and 183 Little Lonsdale Street and in Collingwood, purveying ‘every variety of cheap and useful Goods in the Linen, Drapery and Grocery business’. He expanded into the Tasmanian market in the 1860s and 1870s, and by 1885 had crowned his career by establishing the ambitious retail partnership of Craig & Williamson’s in Elizabeth Street, Melbourne, effectively a large department store. He retired a wealthy man in 1887, and settled with his family at Rangeview, a pretty house in Mary Street, Kew.