By default, when you create a Roll-Up, we automatically set the creation date of the Roll-Up to the creation date of the oldest source website. This can become problematic when you have high traffic websites and archiving the reports for dates in the past would take too long. You can prevent the generation of reports in the past by going to “Administration => General Settings” as a super user and disabling the setting “Synchronize creation date”.

Previous FAQ: Why are URLs in the action reports not linked when I view a Roll-Up actions report?