This may be a totally absurd idea (remember, I'm not sure I understand the problem), but if you need two subnets, why not bridge the Rogers modem, then get a fancier router (I don't know how fancy you'd need to get) with two interior interfaces.
Then set up the fancy router like this:
- WAN port - Rogers
- LAN port #1 - 192.168.150.1 - connected to one network
- LAN port #2 - 10.10.10.1 - connected to other network
... and the fancy router NATs traffic from both subnets to the outside, while allowing traffic to be routed between the two subnets without NAT.
This would be easy enough to do with an x86 box running Linux, FreeBSD, etc. and three NICs. If you're trying to use something more specialized, I don't know who makes software that would let you do this. Maybe the Tomatos and DD-WRTs of the world do...