@Kamaina22 the second picture looks like the root is healthy. The last picture does look like it is soft but could be dehydrated the plumeria is not taking roots since it is entering dormancy. If it is green but shriveled and roots are still looking like the 2nd photo, I would think it is just dormant. It is normal for it to shrivel. I would refrain from watering it if dormant, especially if kept indoor, being in a wet soil will make it rot. I normally would keep the soil bone dry around this time of the year.
If it is black and squishy, chances are it has rotted but make sure it is before you take a drastic step.
