You could create a layer for each mic at the top level. Then put the round robins inside them. Then you can control the level, pan, mute of the 2 main mic layers.
Did you record the samples with multiple mics at the same time? The problem with this approach could be that depending on how you set up the layer alternate module, you might get different round robin sample for the same note.
Or you could create the mic layers as the last sublayer inside the rr layers. But this will be much more complicated to control the different mic layers.