The irb interface is assocated with some vlan and physical ports as well. So without physical ports that are up/up the irb interface will be down.
From your description I think the interface you want is the loopback interface. These are lo0 as the name with units
set interface lo0 unit 0 family inet address 192.168.1.1/32
set interface lo0 unit 1 family inet address 192.168.1.2/32
And then put these interfaces into your routiing instance