Phone Interview - Done within 30 minutes as it was more based upon my qualifications and why I wanted to apply at Riot. Consider this the screening process, rather than the actual interview. It's just to separate the definitely-not-qualified from everyone else.
On-site interview - They flew me in from East Coast for free, along with free night at hotel, within walking distance of company. Not everyone can ace this, even if qualified. The best way to describe it, is like a country club. Either they really love you and offer you the job the day after, or they just never call back. This interview is not based on qualifications. Instead, they wanted to see two things from all interviewees, if they have passion for the company/game (which is mandatory) and how much potential you have. This applies to all departments at Riot, not just Player Support as I found this through their talks on GDC vault (watching their videos help). For my interview they cut it down to around 3-4 hours.
Sadly, I failed to deliver on my potential future as I am a recent undergraduate.