Finding the IDs of roles without any moderator permissions.

Hey, so there's this guy in my server who keeps finding the IDs of roles in my server and also pings unpingable roles using their IDs. Some of the roles aren't even attached to any member. I find it pretty cool and I'd like to know how to do it myself. I've asked the guy but he just replied with a ";)". Does anyone know how this madlad does it? Or is it just magic lol.