What are the responsibilities of a Development Manager?
What are the responsbilities of an Accounting or Finance Manager?
What are the responsibilities of a Marketing Manager?
Generally, I'd say make sure their people have the opportunitiy to do good work.
* to get silly obstacles out of their way;
* to make sure they have the tools needed to do their job properly;
* to make sure that they understand completely what their jobs are and have the opportunity to execute them;
* to make sure their people are trained with current techniques and practices and have the opportunity to exercise them;
* to make sure their people know what is expected of each of them, and what is needed to advance in their career and profession.