Roles are very much still in development, and are only used currently on the agent side.
For the client portal, you can mark a contact as billing or technical. Billing let's them see quotes and invoices and setup auto pay. Technical let's them see all tickets, manage other contacts and see certain shared documents.
We will probably expand roles to replace technical/billing contacts in the future but for now the technical/billing bullet point in the contact page docs is still accurate for access.