The answer is No, you cannot roll back changes once you run Aggregate Inventory Transactions per Period.
1.) Create a transaction, but do not transfer it to GL.
2.) Execute Aggregate Inventory Transactions per Period (so the transaction in checked as being ‘Incl Part Aggr per Period’)
3.) RMB on the transaction to ‘Modify date applied’ the error ‘The Transaction is Processed by Inventory Statistics Update. Data cannot be modified’ appears.
In APP8 with Bug ID# 104595, R&D introduced a Cuttoff Date for Aggregate Inventory Transactions per Period.
I tell my IFS customers to run the Aggregate Inventory Transactions per Period, with a cutoff date 1 day prior to the period end. This way you still have and opportunity to modify your data, on the last day of the period.
Please let me know if this helps to resolve your issue, or if you need further assistance.
One more thing, for your existing data that you cannot change, see if your finance department can create manual journal entries to move the accounting / money from one period into the newest period.