Permissions allow staff to perform certain tasks like sell something for free, or create a subscription.
Custom Roles allow you to add or remove specific permissions for multiple staff, by creating and assigning a new custom role (ie. Front Desk Plus').
You can create and edit new custom roles and bulk assign them to staff members by heading to Settings > Staff Management > Roles.
Name your role, then choose what it can do. Consider starting from another role, to save time. This will fill out all the permissions enjoyed by that role. You can then edit them as needed. Then assign staff on the following page.