Please make sure that a Mix-Minus is being used. On the Rodecaster, it is also important to select the Rodecaster Pro Stereo input and NOT the Rodecaster Pro Multichannel input.
The Mix-Minus feature can be enabled in the settings of the hardware. This feature will eliminate any chance of echoes being present on your recording. On the 2.1 firmware of the Rodecaster, the option can be found in:
More information from Rode's site:
Switchable Mix-Minus on USB Main Output
The RØDECaster Pro now has switchable mix-minus on the USB channel, in addition to the mix-minus on the Bluetooth and TRRS channels. This means if you want to connect a computer-based communication app like Discord or Skype via the USB channel, you can do so without a feedback loop. This is also activated via the ‘Advanced’ menu.
An important note to remember: if you activate mix-minus mode on the USB output, the main USB output no longer represents the full podcast mix. This means if you want to record the stereo mix to your computer as well as use the USB input for a phone call or similar, you will need to activate multitrack mode. Make sure you allocate the main USB device to your communications app, and Source 1 and 2 of the multitrack USB device to your recording software.