Hey everybody, new OPNsense guy here. Got a rather odd type of configuration I'm trying to pull off with OPNsense. Not a network guy by trade, but once upon a time I passed the CCNA exam so I understand routing/networking better than most.

Background: Home has 2 ISP's. I pay for higher-quality fiber service, but my HOA also provides us with a basic cable and internet package from lousy cable company. However, cable boxes / STB's are not part of the package, so either I have to pay extra for the boxes or use a Roku app to use the TV service I pay for through my HOA (how this policy makes sense still is baffling to me). Roku app works great, but only if the Roku devices themselves are using lousy cable company's internet service. Previously, I had a Cisco Meraki setup, where it was very easy to set a 'WAN preference' for certain hosts, and this worked great. Meraki is now gone, and I've moved over to OPNsense after a brief stint with a Unifi USG (still needs a lot of work to become an enterprise-class product, IMO).

I've currently got OPNsense up and running, and am trying to figure out what the best solution is going to be to get what I need out of this. I've got both WAN1 and WAN2 up and working as single gateways with the priorities I want (see: https://i.imgur.com/otLjgLC.png).

Here's a basic diagram of what I'm working with/attempting to accomplish, obviously trying to keep it as simple as possible. Don't want to have to set up VLAN's and separate LAN subnets if it can be avoided:
https://i.imgur.com/Hq4wfEF.jpg

I've read the Multi Wan documentation a few times over, but I'm not sure if Gateway groups is what I really need. Maybe it is. The fiber connection is far superior to the cable one in terms of upstream, latency, and reliability so I only want the Roku's to use the cable connection. It also gives me the added benefit that when I'm using either of them, the fiber connection my PC's use doesn't take the bandwidth hit.

Hopefully somebody can point me in the right direction, as I'm sure that I can't be the first guy to try to pull this off.

Thanks in advance to everyone for reading and helping out!