Roll-up Summary field calculations occur after record-triggered flows, processes, and workflows in Salesforce's order of execution. When a new appointment record is created, the Flow will fire immediately upon record creation, but at that moment, the Roll-up Summary field on the parent record hasn't been updated yet. This means the Flow would send outdated appointment count information to the agent unless specifically designed to account for this timing issue.

A. Roll-up Summary fields work with both standard and custom objects when master-detail relationships exist.

B. Flows can be triggered from both standard and custom object records without restriction.

C. Roll-up Summary calculations do not prevent Flows from being triggered; they execute in sequence.

1. Salesforce Developer Documentation: "Triggers and Order of Execution" - Section on System Validations and Roll-up Summary calculations

2. Salesforce Help: "Considerations for Time-Dependent Actions and Triggers" - Process automation timing

3. Salesforce Architect Documentation: "Platform Events and Process Automation" - Execution order details

4. Salesforce Administrator Guide: "Roll-up Summary Fields" - Chapter on calculation timing

5. Salesforce Developer Guide: "Flow Builder" - Record-triggered flow execution context