Learn English – What does the word “rolling” mean in “rolling grassland”

According to Wikipedia,

Moral luck describes circumstances whereby a moral agent is assigned moral blame or praise for an action or its consequences even though it is clear that said agent did not have full control over either the action or its consequences.

More simply, it is the idea that people are to be held responsible for an action even when they aren't the only force that caused it - even if it occurred accidentally.

This stands a bit in contrast to the typical sentiment that responsibility correlates with voluntary action. (Meaning, if you choose to do something and do it, you are responsible for it.)

There are some interesting problematic examples in the Wikipedia article you might want to check out.

I don't know enough about Gauguin to speculate as to why he's such a good example of moral luck, but hopefully knowledge of the term will make the book's argument clearer in context.

To scalp carries an informal, possibly illegal (unauthorised) , connotation that resell does not:

• (Informal.) to resell (tickets, merchandise, etc.) at higher than the official rates.

Thus usage is from the late 19th century from a practice that became popular in the U.S. with long distance train tickets:

Scalp: (Etymonline)

• Meaning "person who re-sells tickets at unauthorized prices for a profit," 1869, American English;earliest reference is to theater tickets, but often used late 19c. of brokers who sold unused portions of railway tickets.

  • [Railways charged less per mile for longer-distance tickets; therefore someone travelling from New York to Chicago could buy a ticket all the way to San Francisco, get out at Chicago and sell it to a scalper, and come away with more money than if he had simply bought a ticket to Chicago; the Chicago scalper would hold the ticket till he found someone looking for a ticket to San Francisco, then sell it to him at a slight advance, but for less than the official price.]

• Perhaps from scalp (v.); scalper was a generic term for "con man, cheater" in late 19c. Or perhaps the connecting sense is the bounty offered for scalps of certain destructive animals (attested in New England from 1703) and sometimes Indians (i.e., having only part of something, but still getting paid). Some, though, see a connection rather to scalpel, the surgical instrument.

Scalping in finance:

• A trading strategy that attempts to make many profits on small price changes. Traders who implement this strategy will place anywhere from 10 to a couple hundred trades in a single day in the belief that small moves in stock price are easier to catch than large ones.

• Traders who implement this strategy are known as scalpers. The main goal is to buy (or sell) a number of shares at the bid (or ask) price and then quickly sell them a few cents higher (or lower) for a profit. Many small profits can easily compound into large gains if a strict exit strategy is used to prevent large losses.

(Investment.com)