Even if this rock were to hit earth, most would be ablated in the atmosphere. What would hit the ground would be 4m accross if lucky(typically around 90% gets ablated off) Almost all if not all the cosmic velocity would be gone, so an explosion on impact would most likely not occur. So a 4 metre rock hits your roof at terminal velocity of 250m/sec. Yeah, it would make a big mess, but think what you could sell bits of the mass off on ebay for!
Me reckons I could dine out for years on the story. Think of the corny puns- enough to bring the roof down