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Everyone who interacts with the project needs to be in the Users role. Users must also be in the Developer role in order to update tickets. Just having the developer role is not sufficient to view the project. Administrators will also need to be in the User role to view and create issues in a project AND the Developer role to edit and watch issues.
As of 10/8/19, by By default, a new project includes the default system wide group: administrators. The project creator must assign users to the appropriate Administrators, Developers and User roles. Prior to this date, the roles were set by default to the global users, developers and administrators groups. This means that all Jira users in the system can create and view tickets in your project and all developers can edit and watch tickets. If this is not desirable, you can remove those default developers and users groups from the roles and click on “Add users to a role” to either assign individuals to the roles or groups (if you have an existing group for your area).