Is there a hornet's nest on the roof?

It doesn't matter. There's nothing to be particular about.

Kill them.

1. Fire attack. Pour gasoline on the cloth and put the cloth on a long stick to attack them. Bees can't catch you without wings.

2. In rainy days, take a stick bucket and empty the nest. Not bad.

There are often hornets' nests in my yard. I am an expert in dealing with them.