That may be a vet job, and quickly. Infection that gets into bones can go systematic rapidly and kill rapidly too. If you can't afford a vet, you may want to consider amputating it yourself. Or pulling out that bone. It cannot be left sticking out and keeping the infected site open to more infection, and preventing the healing.
I'm Australian, we don't have frostbite issues here, but I did have a hen who received a severe toe injury that left the bone exposed, but thankfully this one cut the bone as well, so all I had to do was keep it disinfected and protected and the stump covered over nicely. I used Stockholm tar. But that's a lot of bone sticking out your roo has there. You may want to start feeding him raw garlic daily for natural antibiotics, or give him artificial antibiotics, to deal with the swelling in his foot.
Best wishes.