I think he means in one roll, not in one turn. If that is the case, the most I can come up with, at least in non-overlord is 6. This would occur in things such as medic/mechanics and such were you role equal to the number of cards you have and which can be up to 6. That is the most I can come up with.
I was thinking attack, but yes, M&M would give you dice equal to Command. Again, most likely 6 but there may be a scenario that goes over 6.
Is he trying to make custom dice?