I remember now -- The Living Theatre.

The theatre of the 20's is understudied -- do you know of the WPA theatre collection at George Mason Univ.? (unless it's been moved to the Smithsonian) A book by J. O'Connor and ? Brown (I forget the title now) would be a good start.

When I think of the Roaring Twenties, I cannot help but think of the movie, Some Like It Hot, or the gangster films with Cagney, Bogart and Edward G. Robinson. Eliot Ness is a fascinating person, as well as his ongoing battle with the mob. Prohibition was huge, and violence was a way of life. I would probably look at the struggle for power during that time; the rise and fall of Prohibition. And I would be equally interested in the history of the mob and how it affected the 20s, reaching forward to modern-day America. I have heard that the Kennedy's (as in John F. Kennedy) fortune was made by father, Jack, in bootlegging whiskey. It was a time of opportunity for some, and hardship for those who were at the mercy of the mob. Mobsters created a microcosm within the U.S., and I would find that struggle for power very interesting, though also dark and violent. Perhaps it might be interesting to compare Hollywood's depiction of this time and compare it to what was really taking place in the big cities.

I think examining the characteristics of the 20's and 30's and how they have influenced society today would be interesting. Examine the impact the language of the periods impacted today's culture, how music has impacted the music of today, or even how there could be a future trend influenced by the period.

Not too many mentions of the jazz aspect of your class, so I'll bring it back into your mix of possible ideas. Looking at the music of the 20's and 30's would let you look at the beginnings of musicians including Louis Armstrong and Benny Goodman and styles of jazz ranging from New Orleans blues to big band swing. Check with your instructor about incorporating video of performers in action along with your 20 pages!

What about the flowering of women's rights?  There are so many things you could explore here...working women, voting rights, changing gender roles.  There are female expatriots, also.  :) 

Since you mention Ernest Hemingway, I would be tempted reread The Sun Also Rises (one of my favorite novels) and consider research about other American expat's living in Paris (or in other parts of Europe) following World War I. You might also want to consider a history of jazz music during the time period or perhaps a history of the Harlem Renaissance.

You might think of comparing the literature preceding the Roaring Twenties or the Great Depression with the literature published resulting from one of these eras, especially that of the expatriates, to see if you can identify a cause-effect relationship in literary tone or mood resulting from either one or the other: Why did literature become so gloomy or depressive or pessimistic--if it did?

You might also want to look at how this time period influenced other time periods.  For instance, how did the introduction of opium and heroine change the course of literature and the nation.  Or, how did the abundance of alcohol despite prohibition influence future eras?  The roaring 20s was a very influential time for many other periods as well. 

The Great Depression was also a very influential period.  One interesting thing might be compare the Great Depression to the current economic crisis.  How did the events that occurred during this time period influence the way we think about and view the current economic climate?  Some of the financial burdens of our country started during (or were a direct result of) the Great Depression.

You might like to think about the way in which literature from the period depicts the Roaring Twenties as experienced by Americans in Europe. This would allow you to focus on some of your favourite authors such as Hemingway, by looking at his book The Sun Also Rises as well as other examples of his fiction. You also might like to consider other fiction by authors such as F. Scott Fitzgerald, whose masterful "Babylon Revisited" would be a good story to analyse.

I don't know if you'd be interested in this, but maybe you could do something about a particular segment of the expatriate population in France.  For example, you could look at African-Americans like Josephine Baker.  Or perhaps American women in general.  You could compare the way they were treated in France with the climate for whatever group you choose in the US at that time.

Love that time period of American history, so there's no shortage of possible topics.  Here are a couple that spring to mind:

The 1920s drug problem - Opium dens proliferated in the late 1800s early 1900s, but our first real heroin addiction problem took place in the late 1920s, on a much smaller scale than today's problems, of course, so it sometimes gets overlooked.  During Prohibition a fair number of people abused drugs instead of alcohol (or in addition).

WPA Music, Theater and Art - A smaller, lesser known part of the Works Progress Administration subsidized artists, actors and musicians to produce murals, works of art, plays and musical shows.  They were often at a local level and represented really the first time the government provided funding for the arts.  Sort of a forerunner to the Nationa Endowment for the Arts.

The Expatriates - I know less about this topic, but what if your research included the "Paths of the Expatriates" to Paris especially, what happened in each of their lives to motivate them towards that Mecca of discontent, as it were.

Good luck!