Rollup to ultimate parent Account from Opportunities

[JSaterdalen]

Hi, in our org we have one Account per customer, with many child Accounts that represent our customer sites. We only related Opportunities to this site level—never the parent Account. So Account > Site Account > Opportunities.

I am trying to sum the Amount from ALL Opportunities related to Site Accounts, and that have a close date within the next 90 days. As a SOQL query, the result I expect is as follows:

SELECT SUM(Amount)
FROM Opportunity
WHERE Account.ParentId = '0015e00000PzFAnAAN'
	AND Close_Date_Next_3_Months__c = TRUE
GROUP BY Account.ParentId

That gets me $236,996.96 from 3 opportunities, across 2 child Site Accounts.

However, my rollup triggered on the opportunity doesn't get the sum from ALL opportunities in this hierarchy. I don't need to store the sum on the child sites—only the parent Account.

Do I have my rollup setup incorrectly for this?