I wanted to provide a bit more information about the environment. There are 3000+ subsites and most sites have on average 3 – 5 lists / libraries that will have content that could be included. We are looking at design architecture options that will efficiently scale. We are open to setting up a set of master lists that would be used to collect the information involved in the rollups, but this would add complexity to our design. We are intending on using a flag within our metadata to mark content eligible for the rollup process. The simplest solution would be to use the web parts to handle the rollups across the site structure, but I am concerned with the overall scalability within this simplistic design.