Multimedia journalism is a pretty nebulous term. As a result, in my experience, when students try to adopt the role two main problems recur: 1) having a narrow assumption of what multimedia means (i.e. video) and 2) not being able to see the multimedia possibilities of your work.
Multimedia journalism is a very different beast to broadcast journalism. In broadcast journalism your role was comparatively simple: you had one medium to use, and a well-worn format to employ.
Put another way: in broadcast journalism the medium was imposed on the story; in multimedia journalism, the story imposes the medium. —Online Journalism Blog.