Assuming the ultimate goal is to get all of your items assigned with the correct GL accounts, I would make sure all items are assigned to an item class and that the GL accounts assigned to those item classes are correct. If you then want to roll down these GL accounts to all items follow these steps:
1) Pull up an item class that is assigned to items and make note of the GL accounts
2) On the item class change the GL accounts to something other that what it currently is
3) Click Save and click Yes to roll down changes.
4) Pull that same item class back up and change the GL accounts to the correct GL accounts
5) Click Save and click Yes to roll down changes.
The roll down will only change those accounts with different values so you need to change them to something else first and then back again.
If the future you may want to create a Business Alert to send you an email when an item is setup with a GL account that varies from its assinged GL accounts in it class.