Charles T. Roberts was trained as a civil engineer in Britain and became an associate member of the Institution of Civil Engineers. However, when he came to the Witwatersrand in 1887 (the year after gold was discovered there) he started designing and erecting machinery. By 1892 he was consulting mechanical engineer to the South African Trust and Finance Company, the City and Suburban Gold Mining Company, and other firms. During that year he became a foundation member of the South African Association of Engineers and Architects and on 5 October read a paper before its members on the "Design, construction and working of air compressors". He drew special attention to the advantages of compressing the air in two stages and of obtaining an air supply at the lowest possible temperature, and pointed out the necessity for effective lubrication of the air cylinder. The paper was followed by a lengthy discussion and was published in the association's Proceedings (1892-1894, Vol. 1, pp. 14-21). The topic must have created considerable interest, for on 29 November 1893 Roberts read another paper on "Compound air compressors" and three days later took members on a visit to the works of the Metropolitan Gold Mining Company in connection with his paper. He served on the association's council for 1893/4. By 1895 he was consulting engineer to the Consolidated Investment Company, Johannesburg.
By 1902 Roberts was living in Salisbury (now Harare, Zimbabwe). He became a foundation member of the South African Association for the Advancement of Science that year and served on its first council (1902/3). However, he was no longer a member by 1906.