Riis met a cross from Brad Potts flush on the volley and found the net to earn a point.
It was the second time Riis had equalised in the game, the Robins having taken the lead first through Chris Martin and then Antonie Semenyo.
Here are the player ratings from the Championship clash, with Riis pick of the bunch.
1. Daniel Iversen 5
The keeper’s kicking at times lacked quality and should he have been beaten at the near post for City’s second goal, however good the shot was? Photo: Camerasport
2. Sepp van den Berg 6
Defended well in patches but there were times he got stretched by the Robins attack, with Semenyo getting past him for the second goal. Photo: Mick Walker/Camerasport
3. Patrick Bauer 6
Chris Martin pulled off him for the first goal but otherwise he was solid. In the second half he brought the ball out of defence well. Photo: Camerasport
4. Andrew Hughes 7
Decent display on the left side of the defence, made a couple of good clearances and got forward well late on as PNE chased parity. Photo: Mick Walker/Camerasport