Riot tends to be less about filling open slots and more about finding people who are compatible with our philosophy and the way we work. If you meet those criteria and are reasonably competent in your craft, there is a good chance we can find a home for you.
The individual team you work on (ranked vs champion vs client vs skins vs live etc. etc.) have much more of an effect on your day-to-day experience than your title as a designer. This holds true for pretty much every discipline at Riot.