I wrote the first version of FindRoots back in late 1999 to analyse HPROF dumps. At the time it was the only IBM tool available for analysing out of memory situations, the only alternative being Sun's own Heap Analysis Tool (HAT). The rather better known HeapRoots tool started life as an attempt by my mate Roland Paterson-Jones to write a similar tool but faster and using less memory. For a while we competed over whose tool used the least memory but eventually our tools diverged and especially since Dave Nice took over HeapRoots has concentrated on being a an interactive tool whereas FindRoots works in a batch report-generating mode. (It's worth noting btw that HeapRoots cheats by doing a simple DFS and does not produce accurate reachability counts. I got sidetracked for a long while by the problem of how to compute the exact transitive closure of a graph efficiently. It's an incredibly complex problem to crack!)
FindRoots introduced the idea of using the dominator tree back in 2003 and this has proved a very valuable approach.
I've been too busy on other stuff just lately to do much FindRoots work but I do have a partial rewrite in the works that promises to be much faster and leaner.