[Hannibal]

It's already prewired, or at least our North American units are.

The blank switch covers below the HVAC controls have connectors plugged into the back of them. Roof power runs up the left hand/driver's side "A" pillar.

Switches from www.purefj.com or www.otrattw.com

Some use Joker Machine Hollow bolt M8x35mm to run the wires into the cab from a roof rack bolt hole.

Roof light wiring, inside OEM rack | Toyota FJ Cruiser Forum (fjcruiserforums.com)

 

[Hannibal]

What year do you have?

Pull the covers and see what you have. Search on here for blank switch covers, lots of threads on it.

There should also be a prewired harness that runs to the front bumper for OEM aux. lights.

 

[Hannibal]

Front only. An optional roof rack air dam with 2 lights were offered. And 2 front bumper lights.

The OEM roof harness is only good enough for the OEM Hella's. What do you want to run up there?

Anything else needs its own harness, relays, etc. and run through the Joker bolt or a Blue Sea marine connector. Some just run the wires down the "A" pillar into the cowl, firewall...

It's easy to Google/Bing FJ Cruiser roof rack lights and most times it'll bring you back here to a selection of threads.

Welcome & Good luck!

fj cruiser switch panel - Bing images

 

[Hannibal]

Highly suggested reading...

Roof Rack Parts List | Toyota FJ Cruiser Forum (fjcruiserforums.com)

Roof Rack Reference Pics | Toyota FJ Cruiser Forum (fjcruiserforums.com)