I cut from Braddock up Kensington, then on a path through Frick.
Then Reynolds -> Beechwood -> Fifth.
(Often Denniston -> Kentucky -> Aiken, etc)
The path in Frick is not long, but I suppose could be a problem if the road bike has seriously skinny tires and/or it rains.
Going From Regent Square to Downtown, I might just go on Forbes -> Schenely Dr -> Bigelow -> Fifth.
The only reason I think someone might chose Penn over Forbes is because their gears aren't low enough, but that's me.
I would also consider Forbes-> Murray -> Bartlett -> Pather Hollow trail down past the lakes. Someone who isn't me (SWIM) might goe past the lake, carry their bike over the tracks and be on the Junction Hollow trail. But, of course, never trespass or break any laws.
So many ways to go! If I did it every day, both ways, I might only repeat once a week or so.