The song "Never Gonna Give You Up" was a single released by Astley in 1987. 21 years ago.
The history (which may be wrong) behind the Rick Roll dates back to when Rockstar released their first Grand Theft Auto IV trailer last year. The official site had a countdown to the trailer. Because so many people were waiting for the countdown to end, the site overloaded. People were scrambling to see this trailer until one person link Rick Astley's "Never Gonna Give You Up".
Similar to a "Duck Roll" where people would be promised something interesting but turned out to be a duck with wheels.
Onward. Just because you heard Astley's song in wherever place doesn't mean it was a prank set up. This song has always been popular and you're bound to hear it now and again.
But for fucks sake it's been a year.
tl;dr you kill jokes long after they've decomposed.