A roulette is a tool that has a small textured wheel at its drawing end. To use it, you roll it over the plate. It makes wide marks that hold ink, and usually they are accumulated to create a tone in a small area of the print.
Roulette
Prints Made Using Roulette
Color spit bite and soap ground aquatints with drypoint roulette on gampi paper chine collé
Color soap ground and spit bite aquatints with photogravure and roulette