In our example, we create a command with which people can toggle a role which the bot would use in the twitter announcement messages. If you want to tag the role, you will need to leave a space between the colon and the at (togglerole: @Twitter) so you get tab completion, the bot will still be able to understand the command, even with that space there. Altearnatively, you can also just type the name (Twitter Notifications) or part of the name for the bot to recognise the role on it's own or, if you have developer mode enabled, copy the role's ID and then just paste that.