Roger's organization received a mass email message that attempted to trick users into revealing their passwords by pretending to be a desk representative. what category of social engineering is this an example of?

The above scenarios is an example of PHISHING, a category of social engineering.

Phishing is defined as an attempt to get confidential information like credit card details, usernames and passwords by presenting itself as a trusted entity in an electronic communication. 

A lot of phishing incidents have already been happening in the real world and lots of money from bank accounts have been stolen because the thief will then assume the electronic identity of the owner and make unauthorized transactions.