Loads simply need to be adequately secured. State (harmonised?) traffic/vehicle regulations.
One start point, although similar advice should exist for each state and territory.
And from the NTC, which is national.
Absent is any advice on using the roof as a load carrying system. If they were bar style roof racks or accessories AS1235:2000 covers these. It explicitly does not cover other types of devices that may be used including any attached by suction or magnetic attached.
Bunnings calling them a ‘soft’ roof rack seems to skirt the regulations. Adequately secured might depend on the mindset of the authority that has you pulled over and how polite/innocent you appear. I adopt instantaneous guilty look in front of any authority.
If there is something not explicitly prohibited it must be OK, until?
Bunnings are load rated for 36kg per pair, Autobarn 65kg. That appears to be the manufacturer suppliers advice. No mention of any standard?