How to add multiple "Forwarding routes" to stock VPN client?
I think you are talking about PPTP / L2TP / IPSec VPN configuration in Settings:



I haven't used that, but according to this source a space between routes should work:


  "In the Forwarding routes box, enter X.X.X.X/X - optionally, you can also enter Y.Y.Y.Y/Y Z.Z.Z.Z/Z (put a space between each entry)."


So this should work:

1.0.0.0/24 255.0.0.0/24


If it doesn't, I'm afraid rooting is the only way. Then you can modify routing policy (ip rule show) and kernel routing table (ip route show table all) as per your requirements.