Rocket Validator looks for accesibility violations on your pages using the axe-core accessibility engine, hosted on our own servers and integrated into our web crawler. You don't need to buy an additional license, everything's already included in your Pro account at Rocket Validator.
WCAG: 2.4.7: Ensure that scrollable region has keyboard access
Elements that have scrollable content should be accessible by keyboard
Checks scrollable content for focusable elements enabling keyboard navigation. Keyboard navigation should not fail when focus moves to an element within a scrollable region.