just FYI, some of the specular channel properties give (sometimes completely) wrong ids when dragged to the console...
Hi @indexofrefraction you should useREFLECTION_LAYER_MAIN_SHADER_ROUGHNESS for REFLECTION_LAYER_MAIN_VALUE_ROUGHNESSLINK and you are right for the second this is REFLECTION_LAYER_FRESNEL_VALUE_STRENGTH
The bug you mention was already reported in How to set a Shader for Roughness ???? and so far have not been fixed. If you want to know the real Id you can take a look at c4d_reflection.h
tx, i just wanted to report it...