My 12 year old son in law brought me a few begonia's from his mothers yard that she didn't care about, and they have been frosted twice now. They don't look THAT bad, just a few burnt/frosted leaves. They are a type of wax leaf, I think, and I planted them in planters and put them with my other plants, and was wondering that now that they have already been frosted, what are the chances they will make it?
Frosted Begonia
I have no idea, but would just baby them along and see what happens. Hopefully you will just have some leaf damage and the roots will still be okay and put out new growth.