JobRoller has the custom post type "Jobs" for job listings and "Resumes" for resume/cv's. Within those you can create as many categories as you like.
Yes, the employer can post job listings and view the resume database, whereas job seekers cannot post jobs, they can create resumes and add jobs to favourites.
There is no option for the job seeker to follow a company, but yes they can "star" (favourite) job listings, see recently viewed jobs, and view job recommendations in their customer dashboard.
Employers are sent applications via email, so there is nothing specifically built into the theme to record application data. There is no option to add notes.
As mentioned above, communication between the job applicant and employer is direct through email via the "Apply Online" button on the job listing page. Thanks.