@127.0.0.2 

Love your handle BTW.

So, think a bit more about what you're asking....you want seamless roaming across all 3 homes, fine. 

To start, general roaming means you don't break your connection to the internet, which would then infer that everyone is sharing the same connection to the internet, which I suspect is NOT what you want, and least not generally.

Now, you could make 'general' roaming, but not seamless, possible if you create the same SSID at each site which I think you have done, and manage all 3 sites from the same controller.

Now, you *MAY* be able to do something like the following:

1. create 3 sites to manage routers at each of A,B and C

2. pick which site (say A) will host the 'seamless' roaming traffic (presumably peoples smartphones), devices like Thermostats and Chromecasts would not need this

3. build VPN tunnels from B to A and C to A.

4. create LANs at B and C with a policy route forcing them through their respective tunnels to A

5. ensure APs at B and C belong to their respective VPN LANs for management traffic...which probably means moving your management VLAN off VLAN-1

6. adopt all APs at site A, recognizing that APs at each site will belong to different subnets, but will be managed in the same site

7. create a 'Roam' SSID on a user subnet which is also policy routed through the VPN tunnels back to A

8. create your local SSID(s), ie LocalA, LocalB on LAN subnets defined on the local site router (you might have to create dummy copies at Site A to allow this via Omada)

What I'm trying to achieve with the above, is that the Controller at site A will manage clients on the Roam SSID like they are all local, which means it will transmit the fast roaming tables etc to those clients that support it and allow them to jump from AP to AP, but still route through Router A to the internet...latency could still be a problem as your clients will be hopping across the internet to get from site to site, but in general IP's and TCP sessions will be maintained...my definition of seamless roaming :)

Local SSIDs would egress to the internet via the local site router (ie would not go across the VPN tunnel to A).

You will almost certainly need managed switches in addition to managed routers at Sites B and C to implement the required policies.

Personally, I would simply connect B and C to A and share one big f4t connection.  You can do this easily with EAP225-outdoors to provide a local ethernet connection at the sl4ve sites.  Of course, if you like but don't necessarily trust, the residents of B and C to surf kiddie pr0n or subversive or hateful sites....well, you'll figure it out.

(and those 4's were not typos...we have a very strict language filter on this site)