The celebrated firm was founded in 1770 in La Chaux-de-Fonds by Samuel Roi or Roy (1746-1822). Following his apprenticeship with Josue Robert & Fils at the age of 16, he moved to Fontaines which had become a clockmaking center. Samuel Roi was associated with one of the Maillardets for a few years before returning to his hometown in order to found his own workshop together with his three sons Henri-Louis, Jacques Louis, and Samuel. The firm specialized in the manufacture of scientific clocks, thus establishing the precision clock industry in La Chaux-de-Fonds. Quickly renowned for their horological masterpieces also outside Switzerland, Samuel Roi was honored in 1783 for the invention of a perpetual clock by the King of Prussia "for his efforts to carry the art of horology and mechanics to the highest degree of perfection".
During the French Revolution, the celebrated watchmaker Abraham-Louis Breguet was working in Switzerland and cooperated with Samuel Roi & Fils on the development of decimal, chimney and other clocks. Such clocks, marine chronometers and most notably three-wheel weight-driven clocks, including a three-wheel weight-driven skeleton clock with compound pendulum, Republican and Gregorian calendar and thermometer, were made to Breguet's design by the manufacture and delivered to Paris. It appears that Breguet invited Samuel Roi to work for him in Paris but he declined, see Swiss Timepiece Makers 1775-1975 by Kathleen H. Pritchard, p. R-94.
The Musée de l'Horlogerie in La Chaux-de-Fonds owns a regulator clock by Samuel Roy & Fils, made in 1780, which was displayed at the National Exhibition of Horology of La-Chaux-de-Fonds in 1881. This quarter repeating 8-day clock is considered a horological "tour de force", comprising a single wheel without pinion, indicating hours, minutes and seconds, the numerals arranged in a spiral which a single hand follows, automatically elongating up to 12 o'clock.
In 1804, Samuel's oldest son Henri-Louis took over the management of the firm.