我先举几个介词短语作宾补的例子：

I found him in trouble.

He imagined himself on the point of death.

He didn’t want me in danger.

以上三个例句的介词短语均表达了宾语的状态，所以是宾补。而您给的句子：I invite her to the party. A gust of wind swept the bed off the roof. “to the party”,”off the roof”在句中不是宾补，就是状语。