We had some really cold weather here this year in San Diego and some of the plants looked less than acceptable but my tonic and I gave it to a potted Rosemary that I've had for years and sounds like yours. In a gallon of water a small amount of liquid Kelp and a tbls. or two of vodka which rejuvinates anything, and today there is green and also blue flowers on my Rosemary that was also looking a bit crunchy.

I've had great success rooting cuttings from sprigs of rosemary purchased from the grocery store. It's an inexpensive way to have your rosemary and eat it too, lol... Here's how: Buy a bunch of cut rosemary. Cut off 1-2" of the tops. Cut where the stem transitions from supple green to woody. Dip the cut ends into some hormone rooting powder. There are many different brands, inexpensive and widely available at your nursery: Stick the cut ends into a pot of well-wetted potting soil. (I usually put six or eight to a pot; wet the soil BEFORE you put the cuttings in.) Put the pot in the sun and keep the soil well-dampened but not soaked. Your cuttings will root. As they do, lessen the watering. Remember, rosemary is native to hot, dry climates. In the meantime, use the rest of your rosemary sprigs for cooking. Yum.

A tip about "sunny windows": Glass (even insulated glass)transfers heat and cold quicker than a wall (especially insulated walls). No matter what plant you have in the window, always keep it about 12 - 18 inches away from the glass. No matter what plant you are over-wintering, occasionally spray the foliage with water - just like skin, the leaves need cleaning and hydrating. When watering the pot, sit the pot in a sink with an open drain. Pour enough water to soak through the pot and allow to drain thoroughly before returning the pot to its saucer. Do not crowd your plants in the window - poor air circulation can do as much damage as too much/not enough water. To give plants extra humidity, line a fairly large old pan with rocks or gravel and add water. Place your pot in a clay saucer on top of the rocks. This will provide a more humid environment without getting the plant's "feet" wet. This is good for basil or other more tropical-type herbs that you are growing in winter. The "dry" herbs (rosemary, thyme, etc.) don't need the constant humidity, just the occasional misting. My Christmas tree rosemaries were purchased 2-3 years ago and do just fine outside in our zone 7. When we lived in zones 4 and 5, it was necessary to bring rosemary and some other herbs inside in winter. When we moved here almost four years ago, I brought a five-year-old rosemary from zone 5 to zone 7 - what a luxury not have to bring that big old thing in every year! I get seed in abundance from it every year.

Agree with lazygardens. I, too, am tempted to take out ours in Las Cruces, which look terrible after the record cold, but large specimens shoud probably be 'root hardy' if not 'large stem hardy', so I am going to water a bit and wait a few weeks, then if they are alive just cut out the dead parts. With a large root system, the plants should theoretically recover quickly. I haven't had experience with such prolonged record cold, so patience is required for now (not my strong suit, I should add).