I tried everything.
IIRC, I believe you can only do it in 1 specific place in the entire game -- or, at least, where doing so would actually matter. I'm not sure if you have to drink alcohol beforehand (but hey, it's Roehm we're talking about here -- why WOULDN'T he be drinking?)
I can check on this later when I get home and review my notes...
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OR, do you mean the actual act itself? Again, go to the [only?] spot in the game where it's permissible, then click the Hand Icon on Mr. Roehm when he's in the correct area.