After the activation of the Multiple Profiles for Vendors add-on, the administrator will find a new role added to the list of user roles in the Roles section of the store’s Admin area (Users > Roles) - "Vendor staff":
This role corresponds to access permissions that enable a user to access a specific vendor area and perform operations on the vendor's behalf there. The exact scope of access permissions that a user with this role gets (full or limited) is defined by the vendor.
Note that the "Vendor staff" role is the primary feature of the add-on and hence cannot be removed. If necessary, however, the store administrator can rename it: