Wait... So when you que up what are the roulette options you could be put into?
Just... randomly match you with a party from one of the two deep dungeons?

Full runs can take hours and hours. Would there be a way for a party that had previously been matched to meet back up to do the next leg of their run?

Would you do something to try and incentivize people to do something other than just run early floors for exp and then disband?

And why do you think a roulette would be more successful than just adding more rewards to the deep dungeons themselves?