special assessment

You would need to read the governing documents for your association (Covenants, CCRs, Master Deed, etc.) to see if they require membership approval of a special assessment. Some states have laws governing this but I have no idea about NC.

Also read them, probably your CC&Rs (AKS covenants,declaration) to see if th Board can levy a special assessment up to a certain amount. After which it would need an owners vote. Your State also may have such a s limit.

Normally yes, although some states/communities require homeowner approval for assessments above a certain amount.

As Dean noted, your assessments have been too low for too long, and now the association does not have the funds needed to replace the roofs. At this point, your alternatives are:

* Let the roofs leak, and then pay for the resulting damage on top of replacing the roofs (costs more than replacing the roofs).
* Levy a special assessment to replace the roofs.
* Take out a loan (this is basically a special assessment with fees and interest tacked on - and if an association's finances are too shaky, they may not be able to get a loan).

There are no other options.

This, dear readers, is why I'm in the process of boring our membership to death about why low assessments are poor money management. Worse, there comes a point where the financial hole is so deep that owners literally can't afford to maintain their homes any more. We're seeing that in number of Florida condo communities right now. After the Surfside condo collapse, the Florida legislature passed laws that are preventing communities from kicking the can down the road anymore. Owners are being hit with $40,000 - $50,000 special assessments, and many can't come up with the money. And their is a glut of condos on the market as people try to sell their units and so they're stuck, at least for now.
It's bad.