Rebecca Ross has a couple distinct series and standalones, so picking a starting point really depends on what kind of mood you're chasing. Honestly, if you're a fantasy romance person who loves a slow, intricate build, her 'Elements of Cadence' duology ('A River Enchanted' and 'A Fire Endless') is the obvious launchpad. The world-building with the spirits of the isle and the tense clan politics is just so richly done, and the central romance feels earned.
But I see a lot of folks jumping straight into her YA fantasy 'Sisters of Sword & Song' as a quicker entry point—it's a standalone with a strong sisterly bond and a quest narrative. It's less dense, which can be nice if you're not ready for the full atmospheric commitment of Cadence. I started with 'The Queen's Rising', which is her debut, and while I enjoyed it, the pacing felt a bit more conventional compared to the lushness of her later work.
For a complete detour, 'Dreams Lie Beneath' is a cool, standalone with a dreams-and-curses magic system. It's a good litmus test for her prose style without locking into a series. Personally, I'd go Cadence first, but you can't go wrong dipping a toe with one of the standalones to see if her voice clicks for you.