After install, iPhoto has broken up my rolls into lots and lots of "events." I have been clicking the arrow of each one so I can contract them (a personal preference of mine). What a long process it could have been. I looked for a menu item to do this, but no such luck. As fate would have it, I held down the Option key while clicking on a triangle, and all the events collapsed.
[robg adds: This mirrors the behavior of the previous implementation of "rolls," but I felt it worth mentioning.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070809091205291