Tracking changes to roll up amount fields

Has anyone developed any solutions to track/report on field history of the roll up amount fields on journal entries, payables, billings, and/or sales orders?

Since these are roll up fields, Salesforce doesn't allow for tracking history and since they roll up from objects that are details in a master/detail relationship, we can't even run reports on field history from those objects. 

We're thinking of solving this by creating shadow fields on the JE, Payable, Billing, and SO objects with a flow that updates the shadow field with the value of the rollup field when that rollup field changes then tracking history on the shadow fields. But wondering if anyone has come up with any more efficient/elegant solutions.