Generator start power source varies by RV manufacturer and model - some use the chassis and some the house. Likewise, whether or not the chassis battery(s) are charged from shore/generator power depends on the manufacturer and his power system design. If you have a Monaco, I'm pretty sure it does charge the chassis when on shore power or generator.
And you do have an Auxiliary or Boost start switch somewhere on the dash that will couple the house batteries to the chassis for emergency starting.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC