Question Altering the Root Node via script

Hi Guys,

Just wantign some help im batch importing and was going to use the postprocessorasset method to alter the settings ive managed to alter most but struggling with the ROOT Node, can anybody suggest how this is achieved in code: https://i.gyazo.com/eb65d00b2fcf3c04ad6dbd53babfb702.png

My Code currently:https://pastebin.com/rrZWT0w9