Hi, sorry if this is obvious, maybe I just missed this point, but is Lisa actually married to Roat? I know they are at least drug business partners, and he at least pretends they are for the charade in front of Audrey Hepburn. It's been awhile since I've seen this movie, so I'm sketchy on details.
Yes, I remember that line, but I don't think that necessarily indicates they were married. Perhaps he was just eluding to the story with Lisa being Mrs. Roat earlier in the film when he was disguised and trying to trick her. Was Lisa just his business partner?
In the play, Mike and Carlino both know Lisa very well. It is obvious through the dialogue that Roat does not know her very well. Wouldn't he know his own wife?
When Roat discusses Lisa he is always talking about something she "told" him. However, he has already killed her and she is in the closet in the next room as he is explaining this. It comes out later that Roat killed her after he tortured her to get her to tell him all of the information that he discusses with Mike and Carlino. Why would he torture and kill his wife?
Lisa being his wife doesn't serve the story. Lisa being his drug partner does. He killed her so that he could take what was in the doll and not have to split it with her. He does the same to Mike and Carlino. His motives are simple. Get the heroin and move on.
When asked why he killed Lisa, Roat's only reply is : "Lisa was too clever Mike. I felt certain she knew where it was (the doll)- and then - too late." (dialogue taken from the play)
The movie doesn't really work out the kinks as well as the play.
He explicitly says he has no known associations to Lisa when explaining how he won't be suspected of her murder, so they definitely were not married. At most, they might have been an item (the script does imply Lisa was flirty with Mike and Carlino when they worked together, so this might have been the same deal with Roat-- but that's conjecture), but it's never specified. All we know for sure is that they were business partners and she wanted to run off with the goods.