Every day I see more evidence that our roles are shifting, from copywriting only to the more complex work of content marketing, content strategy, and content management.
If you are new to these roles, two recent books will give you a good overview of the job activities and requirements.
I recommend first reading The Web Content Strategist's Bible by Richard Sheffield. It presents solid information about the nitty-gritty work involved in this job.
Then, read Content Strategy for the Web by Kristina Halvorson for ideas on framing content management in the business prospective that will appeal to the executives who need to approve your budget.