how to keep user account in "Active" status and which role is required to approve requisitions

Summary:Hi, Recently we had an issue, user account got deactivated automatically due to roles not was not assigned. Now we got some information that without assigning roles user account get deactivated. We need some inputs- 1.which role is required to approve requsitions ? 2. Do we need to create any custom dummy role, if yes please suggest while creating custom role which role category and what we need to add under Function security policy. We just need user account should be able to access BPM worklist/via email to approve requisitions without any additional subscriptions.

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