When do I cut back mexican heather, rosemary and ixora that froze in our recent 10-12 hour 20 degree weather in San Antonio?

I would mulch it heavily and not cut it back until late feb or so. I doubt the heather will come back.

I would not think the rosemary would have any damage. If left neglected here in Dallas County, it grows quite large regardless of the weather extremes. I had one of those little Christmas rosemary trees in the far corner of the yard, and within three years it was about 5x5. I have no experience with the other plants you mention.