License requirements for just approving requisitions and purchase orders

Summary:

We need approval routing for requisitions and PO change orders to go through job level based approval hierarchy. There will be several users in the hierarchy who dont need any other access in the system apart from approving the requisitions and POs.

What minimum role is needed to accomplish the same without invoking any additional license cost. If just Employee role is given and a person record is created for the user, it generally is sufficient for approvals but does this trigger any license cost for SSP or Purchasing?

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