Regarding Roma's monolgue with James Lingk in the Bar Scene...

That was the point really. Roma basically put Lingk, an emotionally weak man, into a trance with his dazzling, hynotizing monologue, luring him into a false sense of security. Only when Lingk was fully under his spell did he even bring up the idea of purchasing land

Divided They Fall
 Captain America Civil War 
5-6-16

Roma was the top salesman. He could hook a mark just with inconsequential conversation "they say it's so hot out there that grown men etc etc", scraps of his (supposed)philosophy of life - appear the least salesman-like but gradually introduce talk about attitudes to risk taking, investing - all the while seeming disinterested. The Jonathan Pryce character was weak naive conventional under the thumb of a controlling wife and and wanted to hear about Roma's liberating-sounding philosophy of life, so different to his own. Roma contrived to make investing in real estate seem a liberating act, one thing Pryce could do without his wife's permission. Roma tricks Pryce into thinking that he could change his mind anytime, the cheque would remain in his desk - in reality it went straight to the bank for cashing. Another deal done and a Cadillac Eldorado for Roma.

I love this film and think it's a great adaptation. However, this scene is probably better designed for the stage.

In the stage version we see three scenes in the first act. The first is Shelley trying to get Williamson to give him a good lead (and mentioning Roma as the top of the board). The second is Moss trying to get George to rob the office (Moss is clearly jealous of Roma while George holds him in some kind of awe). Then comes scene three: Roma and Lingk, except when we first see the play (and on subsequent viewings if we are willing to go with it) we don't know its Roma. Pinter is an influence on David Mamet and at first this scene feels Pinteresque. It seems out of place and is essentially a monologue presenting a philosophy on life. Maybe even a convincing one. It feels divorced from the previous two scenes. We might even start to think of it as an attempt at profundity ... And then near the end we get the line where Roma introduces himself to Lingk and we suddenly realise that this is the man we've been hearing about and that this philosophy is just sales spiel. If you listen to the audio play version (with Joe Mantegna as Roma) you can hear the audience laugh when he says his name and the joke is more apparent.

I think this film (and play) is the most successful realisation of Mamet's own apparent philosophy on life: Everybody has an agenda. The scene in the second act where Moss is laying into Roma is clearly fuelled by his jealousy of Roma but is also part of an act so Moss can leave and go work for Jerry Graff without arousing suspicion. The two combine and it becomes hilarious.

I don't understand why Mamet changed the original ending which underlined all this even more, where it turns out that Roma's pitch to Shelley about them working together is yet another con whereby Roma can get half of Shelley's sales (as his partner) but won't have to share his own. You realise that Roma must be angry that Shelley is seemingly going to win the contest after jag-off John blows his latest sale but is trying to get back on top.

I'm straying off topic but I've got to mention the final beautiful irony of the ending. George is the one person who makes a moral decision in the story (not to rob the office). As a result he's rewarded by being able to keep his job (Moss and Shelley are going to jail) and yet it seems clear that the best thing that could happen to George is that he leave that job. He does the right thing and keeps his job as a reward but keeping that job is poisonous. It's fitting he has the last line, saying how much he hates his job.

It's just a bunch of ideas about life Roma had, some real, some made-up, that he thought would impress Lingk.