Jason:

I'd bury them in the ground. Then if you have some leaves or mulch, cover with that. Sounds easier and better than inside any kind of structure. Certainly no heating blankets. They might start growing in mid winter.

I have two root stocks from fig trees which is not self pollinating and need the fig wasp for pollination. The Fig wasp does not live in the cold northeast. I am planning tom propagate one for cherry tree and one for fig tree, I am keeping them inside my garage no heat.

You can overwinter the rootstock outside. Dig a shallow hole and leave what was dug out on one side of the hole. Lay the roots into the hole and backfill the hole with cedar or fine pinebark. Cover all with the mulch and water it in making sure to get mulch around all the roots. Bury everything in leaves at least a foot deep. This should keep the roots moist and protect them from harshest freezes. Bailey is pretty winter hardy so this should keep them quite nicely. Watch for animal digging activity over winter. Rodents love to chew the young roots.

Thank you for all the helpful replies.
Happy growing.
Jason