Ola,
Usually on the front page, students are not students. They get that role assigned in their courses. This way instructors can be students in a professional development course but teachers in their own courses. On the front page of a Moodle, everyone has an authenticated user role. Some modules can be set up with permissions so they will work on the front page with Authenticated User given permissions, but some (especially quizzes) haven't seemed to work that way. Not sure about forums. You can try adding that role to your forum and see if it works.
Hope that helps.