Input/Output level via USB/Rodecaster Pro

Hi all, hoping someone can help here. Current setup is Rodecaster Pro via USB to Macbook. One mic to input 1 and headphones to monitor line 1. Track is recording audio, however I now cannot listen to playback. 

What should the input/output be assigned to? 

I plan on recording a podcast. Not sure if the setup will be 2 mono tracks for each mic? 

or a single stereo track(interview). 

Appreciate and help. Thanks. - Paul