Programmatically Add Features for Role assignment in Ubercart Drupal 7 product node
Don't do that. Inserting into the DB directly can cause you problems down the road; there's already been code written to do what you're trying to do.

Look at the uc_roles functions/documentation and follow how it adds product features via uc_roles_feature_form_submit submission handler and its uc_product_feature_save() call.