Roller in-line hockey uses the same type of puck equipment that is used in traditional ice hockey. According the the USA roller sports Official rule book for inline hockey:
Rule 13.1 – Dimensions – The puck shall be made of plastic, or other approved material, one inch (1’’) thick and three inches (3’’) in diameter. All pucks used in competition must be approved by USARS or the local league.
The Official Rule Book For Inline Hockey – http://image.aausports.org/dnn/hockey/pdf/USARSRuleBook.pdf
Photo 1 – www.funlandchico.com
Photo 2 – thehockeydepot.com