Narrator/Mysterious Man Cinderella Red Riding Hood Rapunzel/Jack's Mother/Cinderella's Mother Florinda Lucinda Jack Baker Baker's Wife Witch Cinderella's Prince/Wolf Rapunzel's Prince Granny/Stepmother Steward/Milky White (if casting with human)/Cinderella's Father (if using)
This is the best you'll do probably since a lot of the time, there are large ensemble-type scenes where most of the characters are either on stage at once or are ready to come on as soon as the other exits. It all depends on what way you're staging the show - if you're staging it in a minimalist, bare-space sense, you can afford to have actors quickly change one aspect of their costume (i.e. for Granny, simply putting a robe on etc.) as opposed to having elaborate changes.
Narrator/Mysterious Man The Baker The Baker's Wife The Witch Cinderella Little Red Ridinghood/Rapunzel/Cinderella's Mother Cinderella's Prince/Wolf/Lucinda (in drag) Rapunzel's Prince/Cinderella's Father/Florinda (in drag) Jack's Mother/Granny/Cinderella's Stepmother Jack/Steward
The Fiasco production had 10 actors. Not sure about the exact breakdown but it was something like this: 1) Baker 2) Baker's wife 3) Witch 4) Cinderella 5) Little Red 6) Jack 7) Wolf/Cinderella's Prince/Stepsister Milky White/Rapunzel's Prince/Stepsister 9) Stepmother/Cinderella's Mother/Giant 10) Narrator/Steward/Mysterious Man
fiasco also didn't have a narrator, the ensemble split up the lines and they just didn't sacrifice him.
The hypocrites in Chicago did it with 10, correct me if I'm wrong, but I believe little red also played one of the step sisters, the witch also played granny, and Rapunzel and Cinderella doubled.
I'm currently directing a production with a cast of 12. Originally I wanted 10 but I ended up adding 2 extra actors.