This instructions are for Windows but for sure you will find out how to translate this into Mac-language.
To get separate channels in OBS from Rodecaster Pro is not easy but feasible:
1) Install OBS
2) Install Reaper with the option ReaRoute
This will generate an ASIO interface called ReaRoute in your system
3) Install the ASIO plugin in OBS
4) Open Reaper choose Rodecaster Pro Multichannel and select 14 channels:
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5) Then add tracks in Reaper. For example, Mic1 in your Rodecaster Pro is Input 3 and Sound Pad are channels 13 and 14.
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6) Then in the channel add a hardware route to a ReaRoute channel. As an example Mic1 to ReaRoute 3 and SoundPad to ReaRoute 13 and 14. You could use ReaRoute 1, and ReaRoute 2 and 3, but I keep same number to clarify:
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7) So now we can use separate channels in OBS for Mic1 and for SoundPad. We launch OBS and add an ASIO Input source and set it like this to add Mic 1:
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8) Now add another ASIO Input for Soundpad cofigured like this:
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9) Now in Reaper we arm to record the two channels (red dot left in the channel):
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10) OBS will look like this:
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11) Last step is to set up Mic 1 at OBS as a Mono channel. Click the gear under Mic 1 and choose Advance Sound Options and the set up Mono for that channel:
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12) DONE, Start streaming or record. If you what to record from OBS in different channels go back to advanced sound options and choose the channels you want:
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I hope this helps.