The Roaring 20s were born out of and a response to the Lost Generation. The Lost Generation refers to the generation of young people who lived through WWI. They suffered many different types of loss - loss of loved ones in the war, loss of hope in the aftermath of the war, and loss of purpose/direction in their lives after dealing with the attrocities they saw. After dealing with so much death, many of them asked "what's the point?" and when they couldn't find a suitable answer, they decided to live in the moment.
Living in the moment meant that they didn't consider the consequences of their actions. They acted rashly, took risks, and gave little consideration to how their actions would affect their lives or the lives of others. The Roaring 20s gave rise to the first fads in in American culture because people weren't interested in investing in clothing or other goods for durability, they only wanted to keep up with the current trends. Which also meant that people lived above their means and entered into great debt. For example, someone might purchase a dress that was more expensive than their budget would allow, because they could buy it on credit. They could take it home now and worry about paying for it later. This is the same mentality that contributed to economic woes later in 1930s. Once the stock market crashed in October 1929, debtors attempted to collect, but people simply didn't have the money that they'd promised to pay. Which led to a downward spiral that touched all segments of society, from banks to common workers.
The people of the Roaring 20s paid little mind to the laws of Prohibition, which made alcohol illegal, leading to an atmosphere of corruption. "Bootlegging," the illegal sale of alcohol, became big business and tied gangsters, businessmen, and politicians to illicit activities in the hopes of making quick money.
One of the more positive cultural influences arising from the Roaring 20s was the fact that disposable income led people to take an interest in art, literature, music, and sporting events. Jazz evolved during this time period, echoing the scattered lives of the generation. This era is the first in which sports figures, especially in boxing and baseball, become heroes to the next generation. Sporting events were a venue that brought people together, despite differences in socio-economic standing, all were cheering for the home team.
The influences, both positive and negative, of the Roaring 20s on the American popular culture are far-reaching and complex, and can still be found today.