Sometimes the management doesn’t understand the meaning of retrospectives. Why is the team spending time talking about problems, although there seem to be no problems, instead of heading into the next sprint? For them it’s barely comprehensible, to hear there are impediments though the team managed to deliver all backlog items they committed to do.
Show them a variety of impediments you discovered in previous retrospectives or ask them to wait for the next retrospective(if it is the first). Important: Tell your team you will show the impediments to the managements and why. Maybe they don’t feel comfortable with and would see it as a stab in the back! Also tell the management they are not allowed to join the retrospective unless the team wants it! The equation the management will understand is:
less impediments == closer alignment == faster and better results
impediments < alignment < return of investment
Also important is a team, who understands the retrospective as something they want and should not underestimate. For example compare the retrospective to a tool they all think is really great or even powerful(in my team it would have been ReSharper). Remind them the retrospective is the time to reveal impediments and get rid of them. If they tell you there are no impediments, ask questions about possible things you noticed in the sprint, which might be impediments. It will make up their minds. The equation for the team:
less impediments == more time == more code they can write ;-)
impediments < time < coding ;-)
For me having retrospectives is one of the most important things in Scrum. But more important than having retrospectives is having good retrospectives. Be prepared and make up a good plan for the retrospective. Create a timeline with different tasks for the team to get the best results. If you want to know more about retrospectives or want some example of things you can do in retrospective I recommend Agile Retrospectives Making Good Teams Great by Esther Derby and Diana Larsen. The book helped me a lot and my team loved to do retrospectives after I read it. There is also an active retrospective Yahoo group.