I am in 6b, where 2 weeks ago, we had 6” of snow followed by multiple days of single-digit temps. It’s now been in the 40s, 50s, and 60s, and so help me, some eyes on my plants are starting to sprout. It’s December and there is a 0% chance we won’t have more bitter cold before the end of the winter. How much can my plants grow before this starts to be trouble? I feel like a little nubbin on an eye is probably okay, but is there a point where the relentless freeze-thaw cycle could hurt my plants? Should I do anything to protect them? I’ve had to do spring freeze protection with frost blankets and burlap during late frosts in the springs, but…it’s December!
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Erica: I am in the Detroit area which is Zone 6b as well (I don’t pay much attention to the Zones as I try to buy the hardiest roses I can - Zones 5 and lower. I have experienced the same weather conditions as you. I provide my roses with their winter protection at mid to end of November. This consist of cutting back the bushes to approximately 2 feet tall and then mounding each with about 10 inches of good grade fine pine bark mulch or soil. After that they are on their own. In the spring (late April) I start to un-mound the roses and typically I find that the canes below the mulch are fine - green and ready to go but depending on the severity of the winter the cane portions above the mound that were exposed all winter usually have died back. I cut back this portion of the cane down to where the center of the cane (the pith) is nice white or light greenish white. I have at times had to cut back canes to 3 inches above the soil. In each case the rose bush has bounced back just fine and by June they are blooming nicely.
In your case - Should your roses start to break dormancy It is my opinion that yes if they get too far ahead this tender new growth (buds) will be damaged when the temperature bottom falls out again. However, It is NOT to late to provide winter protection to the rose canes. As you noted. The use of frost blankets and burlap will do nicely. Applying them now is fine and in my opinion preferred. Applying mulch mounds and/or blankets at the beginning of winter protects your roses from the drying winds and insulates them from the freeze thaw cycles we are experiencing. It helps keep the soil around the roses more consistently frozen limiting the possibility of frost heave. If using blankets, I would just make sure that you do not leave them on to late in the spring as it could allow the bushes to break dormancy too soon leading to possible damage from late frosts.
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No advice, just here for solidarity! 
I’m in zone 6a (chicago) and have been wondering/worrying about the same thing. Thanks for asking this question!
Thank you, Duane. I should have specified in my original post, I do winter protect my plants with compost and mulch, and that’s been in place for several weeks. I have used frost blankets closer spring, but never for most of winter—like your plants, once they’re mulched, they’re usually on their own. We’re now (as you know) back more typical winter temperatures, so we’ll have to see if this mid-winter non-dormancy harmed any of the plants. Your comment at least made me feel more hopeful! Will report back…