Wiktionary
a. (context idiomatic English) Suddenly very high or excessive. adv. (context idiomatic English) Rapidly increasing.
Usage examples of "through the roof".
Despite a coat of yellow dust, the first two looked like white-painted boxes on wheels, or little houses, complete with wooden steps at the back and a metal stove-chimney sticking through the roof.
The hero goes up through the roof and alights on the bank of a stream at the feet of his lady love, who is making daisy chains.
I keep him up on the roof nowadays, ever since the break-in attempt through the roof door last spring.
One policeman came back from outside and another left through the roof exit.
Now the dream of every thief in Port Tinarana was bursting through the roof of the library.
If it looks possible, some of us can go into the complex through the roof.