Not sure what zone are you, most of us stop trying to root around this time.
That looks like the stem is dehydrated. Or if the roots stopped growing but not rotted, chances are the plumeria was going dormant. So it will not open any leaves, it will just be a stick until it wakes up in spring.
However now that you cut the branches. You have to let the end cut callous for 2 weeks. To plump it up you may need to soak it in a water with hydrogen peroxide. If they plump up, let the cuttings dry and just store them for planting in spring.
If you update your zone other members in your zone could probably give a better guidance.
