No you’re not covered by strata insurance, so far as it relates to fixing faulty/defective building work.
However if your builder went into liquidation then you should be able to claim to fix the faulty roof under Home Warranty Insurance. It isn’t clear if you have already done a claim under that for the other issues, but the OC has an obligation to fix something that is defective. If they are covered by HWI then they had better get their skates on as time is running – I get very confused re how long you have but in your case it might be 6 years.
As I said, regardless, the roof has to be fixed now the OC is aware of it. Otherwise as has been pointed out you could find yourself in a position where the strata insurer refuses to pay for damage as a result of it.