I found this out when trying to implement jQuery Mobile 1.4.2. There is over 20 different docs where they use the attribute 'role'. After looking into it, this is something that should be allowed by the HTML validator. The validator produces this warning, "Undefined attribute name (role)."

http://www.w3.org/TR/html5/dom.html#global-attributes states "To enable assistive technology products to expose a more fine-grained interface than is otherwise possible with HTML elements and attributes, a set of http://www.w3.org/TR/html5/dom.html#wai-aria can be specified (the ARIA http://www.w3.org/TR/html5/infrastructure.html#attr-aria-role and aria-* attributes). http://www.w3.org/TR/html5/references.html#refsARIA"

this is how it is linked to HTML5 : http://www.w3.org/TR/html5/dom.html#sec-implicit-aria-semantics

also see: http://www.w3.org/WAI/PF/aria/usage#usage_intro

A working example can be found in contacts-mobile-basic