There is no doubt that inlet air is necessary to ventilate the roofspace, however it is a common misconception that eaves vents are the only access to allow air to enter the roofspace.
The facts are that you need a path for the ambient temperature to enter the roofspace and you need an exit for the heated air of the roofspace to evacuate.
However in this 21st century using the science for the study of air and gases in motion - fluid dynamics - convection, airflows and the venturi effect. Newer more effective inlets within the roof covering – the tiled or colorbond corrugated roof have surpassed the eaves vent inlets of the past century.
Having the inlet ventilators within the roof covering further enhances the principles for fluid dynamics, taking advantage of thermal air currents and wind driven airflows from across the roof, which are continual 365 days per annum.
Therefore as long as you have an inlet and an outlet in place anywhere within the roof covering opposing each other they will take advantage of and harness all the principles for fluid dynamics, to remove all the offensive nasties from the roofspace.
So the need for eaves vents has been superceded by the more effective roof covering inlets of the 21st century.