You can bulk schedule resources to tasks using the Actions > Schedule menu item on the task grid. You can also use this feature to schedule a resource to a task without a specific role ('No Role').
When you schedule a resource to a task, resources will also appear in the task's Scheduling tab, where you can enter estimated and scheduled hours.
If you have timesheet entry rules/filter that require a resource to be a task team member (legacy feature), you can update the filter to require the resource to be scheduled to the task. Then, you might consider creating a "time entry" task that you can use for resources that need to charge time but don't want to be scheduled to a task.
Use Actions > Unschedule to remove a resource from a task.