I think there is just a subtle difference in words used here as a "role" is something that can be assigned to a group or user in ServiceNow. Requestor, Approver and Fulfiller are user types. While ServiceNow include an approver role, there is no out of the box role called Requestor or Fulfiller. The Fulfiller user type may have different roles assigned to them they typically require subscriptions. As you say, the requestor type typically doesn't require a subscription. Typically a request would have no role assigned, so they are not "marked" as requestor, they just don't have any explicit rights beyond that of a requestor. In some organizations an snc_external or snc_internal role is assigned and someone with either of those can be any of these user types, but a requestor would typically not have any other roles. The approver type would require a subscription and this has been replaced by the Business Stakeholder subscription.
