A hot seat meeting is where instead of assigning one person to each role we instead assign every role to every person. Everyone comes prepared for every role: everyone has a speech, everyone has a set of table topics, a joke, a word... etc. Then we decide at the meeting by drawing lots who does which of the tasks they'll be doing.
Why? Well, for one thing it's fun, challenging and an opportunity to stretch, but also because it makes schedule the next meeting easy: Who's got a speech ready? Everyone who didn't use the one they prepared for this meeting. Who's ready to be topics master? Everyone who wasn't topicmaster at the hot seat meeting.