Gantt view only

Hello all. I need to allow our upper management to view the gantt chart and add tasks to the backlog, but not make any other changes. Is this possible? I know that by default only project managers can view the gantt chart, but the problem is it gives too much access to people who do not need to have it. I have tried creating a custom role to limit what a user can do, but it does not have an option to allow access to something the gantt chart but restrict the ability to do anything else. I am also not seeing the custom role as an option when I try to add someone (either user or group) to that role.