Job roles do not get sent notifications. Assignments must be made for notifications to go out. Job roles are used for resource planning and are simply placeholders within an assignment that gets replaced with an individual tied to that role during the planning process.
You bring up another issue though, and that is TEAM assignments. We should be able to assign a team to do work and have that team get notifications, especially for low duration, but critical, tasks. Currently you can only set "team assignment to to team" in notifications. Problem is that when assigning a TASK to a team, they may receive that notification WAY too early, and can never receive notification when all predecessors are complete. It would be nice to have TEAM NOTIFICATIONS follow task assignee notification pattern for those instances where a company assigns a team to do work within a project. "https://support.workfront.com/hc/en-us/community/posts/360026607453-More-robust-team-assignment-notifications">I just added an IDEA in idea exchange, feel free to vote it up/comment there . Marty Gawry - CapabilitySource