Are you wanting to run a provider to each router or both providers to both routers?
A provider to each router I suppose is the only way since I'm pretty sure they each will only give me a single circuit.
If you setup the routers with VRRP (aka failover), you can place a switch (can be a single switch) in between your provider's handoff (from cable or DSL modem e.g. ethernet) and each router. When router A fails, router B just simply picks up (via VRRP) and keeps everything humming.
Read the documentation for more detail, but I've done a setup like this (not with RouterOS) and it worked well.
If you have any more questions regarding VRRP, let me know.