Crew roles

Producer

This person is essentially the group leader and is responsible for managing the production from start to finish. The producer develops the project from the initial idea, makes sure the script is finalized, arranges the financing and manages the production team that makes the film.

The producer also coordinates the filmmaking process to ensure that everyone involved in the project is working on schedule and on budget. Without the producer at the helm, films do not get made.

Responsibilities

maintaining contemporary technical skills;

organising shooting schedules - dependent on the type of producer and availability of support staff;

troubleshooting;

ensuring compliance with relevant regulations, codes of practice and health and safety laws;

supervising the progress of the project from production to post production;

holding regular meetings with the director to discuss characters and scenes;

acting as a sounding board for the director;

bringing the finished production in on budget.

https://www.prospects.ac.uk/job-profiles/television-film-video-producer

Director

The director is primarily responsible for overseeing the shooting and assembly of a film. While the director might be compared to a novel's author as a film's primary visionary, he or she would not be able to make the film without the help of numerous other artists and technicians.

In fact, the notion of the director as an author is misleading because it assumes the director, like an author, does everything. A director works at the center of film production, but is inextricably linked with dozens of other people who get the job done together.

Responsibilities of a director

To direct the film

Insure that that talents are doing an excellent job

A director interprets the script, coaches the performers

 Works together with the montagist, etc., interrelating them all to create a work of art.

According to Film Scholar Eric Sherman, the director begins with a vague idea of the entire film and uses this to help him determine what is to be done.

http://www.filmmakers.com/stories/Director.htm

Screenwriter

While the dialogue in a film may seem natural to the viewer, a writer carefully crafts it; however, the screenwriter does far more than provide dialogue for the actors. He or she also shapes the sequence of events in a film to ensure that one scene transitions to the next so that the story will unfold logically and in an interesting way.

Like the producer, the screenwriter's role is generally overlooked by the movie-going public, yet is essential to the completion of any film. If there is no script, there is no movie.

Responsibilities

Screenwriters are responsible for describing the stories in detail, including physical environments and the moods of the characters.

 Films and televisions shows require the use of these scripts. Prior to production of a film or show, screenwriters might produce a synopsis and several scenes of a story.

http://study.com/articles/Screenwriter_Responsibilities_Outlook_and_Requirements.html

Costume Designer

Costumes convey a great deal about the film's time period and the characters who wear them, including their economic status, occupation and attitude toward themselves. Be sure to think about how costuming can show something about the character visually.

Responsibilities

Make sure that all the costume are ready

Make sure that it is fitted to that specific person

Also the props are on the set and make sure there is no hazard involve. 

http://www.centerdigitaled.com/artsandhumanities/The-Roles-of-the-Production-Team.html