The product vision needs to be created by the entire team because even though the product owner will be the person reminding the team about the vision and goals of the project, everybody needs to contribute and own the product vision.
Time to market is essential and projects usually have budget constraints which means that they cannot be developed for a long period of time without producing value to the customers or the company. Therefore, it is necessary to pick what must be created first.
The roadmap informs all stakeholders of the status of the product and what they should expect in the next months in terms of releases. Of course, this is a living document, and feedback from the users or reacting to the market might change the product roadmap.
What used to be a blue ocean for Netflix as the innovator in the streaming services business, has become a red ocean where everybody is trying to get a piece of the pie.