I doubt that your begonias will survive but you could try by protecting the roots from freezing. The tops will die. They are typically considered a disposable and renewable resource in your location.

Read up about your Polianthes; you can easily save the bulbs over the winter in their dormant stage.

I left mine out this year. so I will wait and see if they died out or will come back again. Rosemary & sage is good, so I will wait and see. I really hope they do come back and I do have a lot!

It is pretty easy to determine how well plants might survive over winter. If you Google by botanical name, you will turn up various websites that will indicate a minimum winter zone level they are liable to survive. And because they are being grown in containers and not in the ground and therefore subject to much colder temps from the surrounding air, you want to make sure that they are listed for a hardiness zone at least 2 lower than yours.

So none of your plants would have been expected to survive a "normal" zone 7 winter outdoors in containers without some sort of protection. And since you probably experienced some extreme cold earlier this winter - as did most of the east coast - it is almost guaranteed that your container plants are toast.

my thoughts too. so start from scratch is it, huh?