The Rollback option permanently deletes the data that you import to your CRM account so that you can import the data again. This is useful in cases when the data is not imported properly and you prefer to import the same data again.   To delete imported records

1. Click Setup > Data Administration > Import History.
2. In the Import History page, the import details are displayed below the List of Imports section.
3. Select the check box(es) and click Rollback to delete the imported data.