When you walk into an office to interview with a manager, it's like being given a bit-part in a major motion picture. You will usually not know much about the plot when you arrive, and you must think quickly and listen to find out what is going on. This much you will know. Something here is wrong. Either someone has left, or the company has grown it's business too much for it's current staff.
Managers hate to create and justify job requisitions.
They hate interviewing ten candidates to find one applicant who might work out. They hate staring at all the interviewees and trying to figure out how much they are lying. They have to put all their projects and duties on hold to interview people. They know that whoever they hire will require costly training. Your job as a candidate is to discern what they need, and help the managers see why you are the logical candidate for this job.