I looked at the Roland specs for the CS-10EM microphone/headset. It's made for various Roland recorders R-05, R-09HR, R-07.

From what I can tell the various recorders supply the 2V to 7V (DC voltage) to activate the microphones, which appears to be of the electret or condenser type.

The specs for the RPI-Hat sound card don't say whether the RCA inputs are line level or microphone level, I'm guessing they are line level, which means to use something like the CS-10EM you would need a separate preamp that also supplies the 2V to 7V DC power.

The specs say the microphone's Open Circuit Sensitivity = -40 dB 1V/Pa

which suggests that to get to a 1 Volt level into the audio board, the preamp would need a gain of somewhere around 50-100.

My experience with other audioinjector stereo board (the one with out the volume controls) supports what I have related above.

If Flatmax would shed some light on the actual audio input specs, which I have not been able to find, we would have a better idea of what needs to be done.