says nothing about the front of the vehicle. Reg 90 says:
(1) When on, a headlight, or additional headlight, fitted to a
vehicle must:
(a) show only white light, and
(b) project its main beam of light ahead of the
vehicle.
(2) Headlights must be fitted to a
vehicle so their light does not reflect off the
vehicle into the driver’s eyes.
The 600 mm issue I believe relates to the low beam (Reg 87) NSW or possibly fog lights see QLD paper previously posted.
There are other regulations about spot lights, but that is a different issue.
The issue about the "front" is only that nothing can be located so it protrudes beyond the front of the vehicle. Of course many driving lights when fitted do offend. If on the roof, obviously will not at least against that requirement.
True there are other issues but generally it appears that LED lights on the roof rack that face forward and do not shine in the eyes of the driver of that car and are turned off when low beam is on, are OK even if one single light bar (but don't quote me).
Of course the NSW Roads and Maritime Services (as it now is) could clear this up with a document on their web site, but I can't find it, so appears we are left to reading the regulations.