Applicability of native semantics when ARIA roles used

Implied default ARIA roles should not be applied to equivalent native HTML elements - this is an HTML validation issue - but it may not be a WCAG violations and in some cases some AT may require it.  My question takes this a step further.  When a role is applied are native semantics still valid?

For example, does alt become the accessible name in this case or does the element below require an ARIA based accessible name.

<img alt="course catalog" role="img" src="catalog.jpg">

That is - by adding the role attribute does that somehow change applicability of the native markup in the accessible name calculation.

Jonathan