Here's a form I use when doing a musical, so that when someone needs to know where to pick up for a certain song, I can give the song number (used by orchestra), song title, script page (director), score page (music director), vocal book page (actor/performer), and who is in it (me!). This particular show had 5 people, so I was able to give them each a column. For a full-size musical, I would simply have one column for actors involved and then list, for example "Laurey and Ensemble Girls" (and if needed, the last names of said ensemble girls).
Erin