I use a similar method with whole class discussion, only I use the roles that we use in lit circles, discussion director, summarizer, vocab enricher, connector, illustrator, researcher.
Students number off and each number has a job associate with it.
Therefore I will have 6 of each role. This really gets the whole class involved. In order to keep track of participation, I use the same method with the seating chart. I cover my seating charts with transparencies and use overhead marker which I can wash off at the end of each wekk. Hope this helps.