Routing two networks with same addressing.

RouterOS Forwarding Protocols
1

We have two networks with same IP addressing LAN 10.1.1.0/24
external IP
R1 WAN 172.16.1.1/30 LAN 10.1.1.0/24 GW 10.1.1.1
R2 WAN 172.16.1.2/30 LAN 10.1.1.0/24 GW 10.1.1.1

Need to link the networks.

2

Link as in LAN on R1 needs to be able to talk to LAN on R2? If the goal is not to bridge the two L2 domains then the best option is to change the IP range on one of the LANs. Might need to know more about the intent to answer this question.

3

Ugliest but doable solution would be to NAT one network to something else and route it after that.

Much easier would just to change one subnet to something else and do it normal way.