It's questionable whether use taxes do in fact pay for the roads.
http://www.uspirg.org/reports/usp/who-pays-roads
One could argue that congress has the duty, or at least the right, to legislate regarding healthcare in the same section 8 of the constitution where the power to protect against foreign enemies is "provide for the common Defence and general Welfare of the United States". I'd consider general welfare to realistically include healthcare.