第一句主句是where is the man,从句是i saw this morning,从句是用来修饰主句中的MAN的,那个男人是我今天早上看到的
句子的必备成分是主谓宾,所以你写的不能构成一句句子
第二句主句是i once lived in a house从句是 roof has fallen in,由于主句的从句是用来修饰主句的HOUSE的,由于ROOF 和HOUSE是从属关系,所以要用WHOSE 连接
补充:这个不是定语从句而是主语从句,the boy who is standing at the door is my brother中,the boy is my brother是主句,who(the boy)is standing at the door 是从句