I think Sam would be great in a lot of roles (just not Nancy!!) I could see her in;
WWRY: Meat
Rent: Mimi
Fame: Carmen or Serena
Chicago: Roxi
JCS: Mary Magdelene
Footloose: Ariel
Miss Saigon: Ellen
A Chorus Line: Maggie or Val
Starlight Express: Dinah (if she can rollerskate!!)
SOM: Liesl
High School Musical: Gabrielle
Sorry if I've stolen other people's ideas there!!
Jodie I could see in
Chicago: Mama Morton
Blood Brothers: Mrs Johnstone
Les Mis: Mme Thenardier
WWRY: Killer Queen
Sweeney Todd: Mrs Lovett
Guys and Dolls: Adelaide (maybe)
Parade: Lucille
I can think of many others, but they might be a little obscure. I think there are loads of parts out there for Jodie, they just take a little longer to think of because they're not the typical "leading lady" roles like Velma or Eponine.
Jessie is the hardest;
Wizard of Oz: Dorothy
Calamity Jane: Calamity Jane
Oklahoma: Ado Annie
Annie Get Your Gun: Annie
South Pacific: Nellie (maybe?)
Beautiful Game: I don't know it at all, but I hear it's for Irish girls, so maybe?
Evita: The Mistress, perhaps...although this song might be a bit high for her. But the character doesn't have any lines...
When she's been to drama school and improved her acting and dancing, she'll be great for loads of parts, but she's not really ready yet.