1 answer
Hi Leah,
You're on the right path of using RollUp Summaries.
You can't use relative date filters on RollUp Summaries, so you need another field on Opportunity to determine the This Year part.
Steve Molis has a great example in the link below.
https://success.salesforce.com/answers?id=90630000000gsl7AAA
So on the RollUp Summary, use the Max Date, and filter by Opportunities This Year by referencing the new field you would have had to create in the step above.
Hope that helps.
--Derhyk