My rosemary and a few other plants winter over on an unheated sunporch. The temperatures in this space usually hover at or above the freezing mark, making it at least a full zone warmer than the zone five outside. This year, however, the cold snap has been so low and so long that I brought all the pots into the house (not before losing two pelagoriums to being frozen stiff.)
I've not had much luck with rosemary in the house. I don't know why, but they tend to die when they are brought in. So this year I will wait and see.
Up here I find the rosemary blooms the last weeks of February of the first week of March, making a welcome promise of the spring that is just around the corner by then.
I hope this year she lasts and blooms for me. Only time will tell.