Thanks Jan,
I couldn't actually see a place where RoleID was findable, but in hunting where to find it came across this query which works better for me, so thought I would share in case anyone else finds this post.
UserID IN (select UserID FROM CMS_UserRole where RoleID = (select RoleID from CMS_Role where RoleDisplayName = 'YourRoleName'))
Not sure if that is more complicated than it need be, but it works.
Thanks again!