The National Council for Voluntary Organisations has some general information on writing role descriptions.
Volunteer Scotland also has a guide to volunteer role descriptions.
As with volunteer agreements, it’s important that volunteer role descriptions don’t in any way suggest that the volunteer is obliged to perform tasks in the way that a paid job description would. This is because it may result in a volunteer being viewed as an employee in the eyes of the law, which should be avoided as it will entitle them to the same rights as one. Find out more on the differences between volunteers and employees via the link below.
Starting with a template that someone else has already prepared may make writing a role description easier. The England and Wales Cricket Board has a comprehensive list of various volunteer role descriptions, which can be adapted for other sports.