Technically, "Roger" means "I have received but not necessarily understood your message" *Laughing Emoji*
Wed, 19 Jun 2019 1:03pm BST
So an emoji is unprofessional but saying "roger" isn't? I would dispute this on the basis of using a non-work based system to communicate. If the rules, stupid as they are, weren't made clear to all employees to begin with the employer shouldn't really have a leg to stand on.