It would be inadvisable to move it if the soil is frozen, but other than that the majority of the dormant season is a fine time. I'm not sure about the root pruning because I haven't tried any of those techniques, but when you do move a top pruning might be advisable to help decrease the water needs for later in the summer.

Root pruning needs to be done well in advance of transplanting - generally 6 months or a full season ahead of the expected moving date. Root pruning is intended to stimulate the development of quantities of fine feeder roots within the confines of the trimmed rootball. To do so now, when soils are cold and root growth is pretty much static, is counterproductive. Also pruning back the canopy or top growth prior or simultaneous to transplanting has been proven to a detriment and increase the potential for transplant shock, even in the dormant season. Removal of buds (or leaf growth, if appropriate) impacts the development and re-establishment of the root system and can also remove a lot of mobile nutrients needed by the tree/shrub until roots are re-established and can access them freely from the soil.

While you will never get all the roots intact with a transplant, you will minimize the damage by allowing 10-12 inches of rootball for every inch of trunk caliper. A Bobcat or frontloader can be helpful; otherwise enlist friends, family or the new owner.

Good point GG, I suppose I was a little misleading there the top pruning should only be done well after the transplanting and once the roots are getting re-established if at all. If I were moving a larger tree now and was forced to cut some of the rootball I would prune some in June or early July to help with the summer shock. Of course irrigation should eliminate this need if available.