The ruling references the Web Content Accessibility Guidelines (WCAG) 2.0 created by the W3C’s Web Accessibility Initiative. The World Wide Web Consortium (W3C) describes itself as “an international community where Member organizations, a full-time staff, and the public work together to develop Web standards.” The complete Web standards for ADA accessibility can be found here.
@Rick, I didn't specifically look at doctype, but Steve Faulkner did in his original article (see the link at the top of this post). He found that 101 of the 130 pages containing role="main" (78%) used the HTML5 doctype, which of course leaves 22% that didn't. I do recommend using ARIA even if using an earlier doctype. Validation is important, but if validation and accessibility conflict, I think most would agree accessibility should trump validation. Assistive technologies that support ARIA landmarks do so regardless of doctype, and otherwise the presence of these role attributes has no ill effects in any user agent.
Finally, WA11Y is another top ADA compliance plug-in to consider. A toolbox of resources to help you meet most ADA compliance needs, the plug-in packs multiple accessibility tools, each with a unique purpose. Tota11y, the first tool in the box, for instance, annotates all elements of your web pages and identifies any accessibility issues. Another tool in the box, WAVE, performs a detailed accessibility analysis of each page and provides printable reports. Then, you have FILTERS which is used to modify data within Wa11y.