Firepower should automatically classify routers and switches using the below logic:
the analysis of Cisco Discovery Protocol (CDP) messages, which can identify network devices and their types (Cisco devices only)
the detection of the Spanning Tree Protocol (STP), which identifies a device as a switch or bridge
the detection of multiple hosts using the same MAC address, which identifies the MAC address as belonging to a router
the detection of TTL value changes from the client side, or TTL values that change more frequently than a typical boot time, which identify NAT devices and load balancers
I do not know if there is a way to get a list of all routers or all switches separately. If you click on one of the ip address in the network device list, it will tell you what it determined that device to be - under the Host-Type section,