You can possibly help matters along by asking your strata manager to arrange a few quotes because replacing one or more roofs will be a large project.
The quotes will provide the necessary data to confirm that insufficient funds are available, and at the very least your strata committee will know what the owners’ corporation is up for and can discuss whether they want to raise a special levy or save up for this work through increased levies over time. Depending on how well everyone knows and trusts each other, you may be able to have a conversation about whether it’s better to save up over time (recognising that if a roof starts leaking, it will have to be addressed with whatever funds have been saved and also the cost of doing the work will increase while you save), or hit everyone with a special levy. If some can’t pay, you can discuss payment plans for those individuals.
It sounds like there is no capital works plan in place, because if there was then this and other items would be on the plan and your levies would be set in accordance with the planned schedule of works. What on earth is your strata manager doing if he/she hasn’t been advising you to prepare a plan? Clause 80 of the Strata Schemes Management Act says that it’s a requirement to have a 10 year plan that is reviewed every 5 years as a minimum. It doesn’t have to be a formal, professional plan. My unit block has a spreadsheet with a list of jobs, the year we expect to do the work and estimates prepared by Committee members. But in your case, if the building hasn’t been properly maintained (which it sounds like it might not have been) then you might want to invest in a builder going through the place and identifying issues that might need to be dealt with in the next 10 year timeframe. You can then put a price on each of these and increase levies to start saving. You could ask the strata manager to put a motion on the AGM agenda that the OC develops a capital works plan.
Another option is for individual owners to take over the job of replacing their own roofs, but I don’t recommend this because once an owner does this, he/she is responsible for ongoing maintenance of that roof.