http://www.cs.cmu.edu/~apd/Pittsburgh/Oscar_Swan_Bike_Rides_Out_of_Pittsburgh.pdf is a good resource.
There are tons of rides at http://www.bikely.com/, too.
50ish mile route with rolling hills?
Anyone have a 50ish mile loop that isn't loade with climbs from the city? I know it won't be possible to avoid hills all together. Need to work on my aero position on the tri bike for about 2.5 hours and I'm clueless where to head b
Head out Freeport Road to the Red Belt, then maybe cruise back to the city on Saxonburg?
Homestead-Duquesne-McKeesport via the trail, then just follow the river through Glassport, Elizabeth, etc. If you go as far as crossing the river to Monongahela, hit the Sheetz, and turn around, it's about a 65 mile round trip from the East End.
Mostly flat, and traffic dies out once you get through McKeesport and Glassport.
The oval?
This one is a favorite and would probably be close to 50 miles if you left from somewhere in Pittsburgh: http://www.mapmyride.com/routes/view/14362800
I should warn that Penn DOT chipped the Allegheny Count section of 380 semi-recently, so there is at times a lot of gravel in the otherwise nice shoulder (the chip treatment stops once you cross the county line).
+1 for Swan