You bought a house and now the roof leaks Does the previous owner need to fix?

Unless you got a guarantee with the house or can show that something was done to hide the problem and can prove that in court, it is your problem. You have to prove the previous owner knew about the leak and did something to hide it. They are supposed to disclose things they know about, but only if you ask. He can say he didn't know about it and you have to prove him wrong. Also, it may just have started.