It didn't sound like it became apparent to the roommate shortly thereafter. According to the article, it was at least a week later, after the Snowden news broke and the roommate apparently became paranoid.

I'm assuming that the report of paranoia and the sentence "I was afraid that if I didn’t end the torture he might need psychiatric treatment" is comedic hyperbole, but I cease giving any "prank credit" after the roommate explicitly and correctly called the author out as the source of the ads.