Regarding software, there are dozen of tools. Search for different content management systems around that suits your and your clients needs.
When it comes to work it depends on how much everyone has to pick up.
I worked in agencies where I was a one man show doing:
graphic design & video editing, content management, community management, ad management, analytics, strategy, project management.
I also worked in agencies where every single field I mentioned above was done by single individuals and experts.