Peter Stevens has a nice write-up on the differences in responsibilities between Scum projects, and traditional project. As can be expected, responsibilities are distributed broader in an Agile team, with much (or all) of the responsibilities of a project manager being spread over the Product Owner, Scrum Master and the development team.
Especially interesting is that they found some responsibilities not being clearly defined in a traditional team (ROI, process improvement), while it was there in Scrum. I’m not sure whether that’s quite fair, since tracking ROI is only rarely actually done in Scrum projects, but the responsibility is explicitly there.
Scrum Breakfast: Responsibilities in Scrum, or Why Scrum Developers Should Get Paid More!.