How to delete taxonomy terms created with entity_generate process plugin?

Question

I have this json.

    {
      "ProductKey": "145.1",
      "Product": {
        "Title": "Product title",
        "StartDate": null,
        "EndDate": null,    
        "ProductKeywords": [{
          "Name": "keyword 1"
        },
        {
          "Name": "keyword 2"
        },
        {
          "Name": "keyword 3"
        }],
      },
   }

So in this case I can't create a separate migration file for the taxonomy terms because the ProductKeywords is an array and have multiple taxonomy terms.

So I have done it in a single migration file with entity_generate plugin for the taxonomy term entity reference field.

keywords:
    - plugin: sub_process
      source: keyword
      process:
        value: Name
    - plugin: entity_generate
      value_key: name
      bundle_key: vid
      bundle: keyword
      entity_type: taxonomy_term
      ignore_case: true

But the taxonomy terms created with entity_generate do not gets deleted with rollback.

I know there is a postRollback migration event, where we can execute some code after rollback. But I don't know how I can know which taxonomy terms needs to be deleted on the rollback.

Is there any example or hint available?