How would that be logical? Why would you run the risk of indiscriminately killing people who might support Roman rule while leaving the people who may oppose you untouched? Especially when you consider that these are the people who you want to pay tax later and work the fields. Even though I don't have any book quotations you can safely assume there was no such practice. Incidents like this would probably have occurred during the long reign of the empire but it was not common practice.