The undefined attribute "role" is an bug with Eclipse WTP (Web Tools Platform) Source Editing. I have the same issue and I'm running Eclipse Kepler EE with a WTP Source Editing version 3.5.2. The Eclipse bug report below has a patch that is targeted for version 3.6RC1.
Update to Eclipse Luna and you'll get WTP 3.6, which includes the fix.
Check your version at Help > About Eclipse > Eclipse Web Tools Platform > Eclipse Web Developer Tools.
HTML5 validation should allow the 'role' and 'aria-*' attributes.
