Yes, my roosters tend to get frostbite in the winters. I've changed coop styles this year, and things are looking great so far. But, we haven't had anything below 10 degrees yet.
I'm not a fan of vaseline. Vegetable oil is much easier to apply. Oil does help. Last year, I couldn't catch a couple of my Red Dorking boys, and their combs fell off in the spring. My oiled boys, just lost their tips. I don't oil my hens at all, and I only do the boys when it gets super cold. If it's 9 degrees during the day, I oil them. 9 degrees at night, I tend to leave them alone.
Frozen wattles where a bigger issue for me, then the combs. I ended up feeding my boys snow instead, and that has helped the situation dramatically.
