high roller vs spender

high roller and spender both are nouns.

Word	Noun	Adjective	Verb	Adverb
high roller	Yes	No	No	No
spender	Yes	No	No	No

As nouns, spender is a hypernym of high roller; that is, spender is a word with a broader meaning than high roller:

Other hypernyms of high roller include scattergood, spend-all, spendthrift.

high roller (noun)	spender (noun)
a gambler who wagers large sums	someone who spends money to purchase goods or services
one who spends lavishly and ostentatiously on entertainment	someone who spends money prodigally