Hello
No the built-in filter is officially not a HEPA filter.
The high-performance filter for Roomba e+i series vacuum robots captures 99% of allergens, pollen and particles down to a size of 10 micrometres.
Best wishes
Your iRobot Team

Fine dust is defined as particles < 10 μm. To be a HEPA filter (filter class H13 / H14), it would have to filter 99.95% (H13) or 99.995% (H14) of particles < 1 μm. With a filter performance of 99% for particles greater than or equal to 10 μm, the Roomba filter is far from a HEPA or fine dust filter.