Rosie O'Donnell -- PARTY MACHINE ... After Show Gets Cancelled

With her TV show cancelled ... her former staff scrambling to find jobs ... and her former network falling apart at the seams ... Rosie O'Donnell partied in Chicago last night ... celebrating her 50th birthday like she didn't have a care in the world.

A smiling Rosie and her fiancee Michelle Rounds arrived to Paris Club around 7 PM ... to a massive line of screaming female fans.

The birthday girl hung out for about 3 hours ... dancing and singing to hits like "Don't Stop Believin" and "The Power of Love" ... we're told it appeared she was having a blast.