Pros
Amazing benefits, great perks which include full lunch and dinner for free, gaming stipend, gym stipend, etc, and flexible working hours. The campus is incredible and the you're surrounded every day by incredibly smart and talented individuals. Lots of opportunity to find a place to add value and contribute what you think is important, and if you're just starting out, tons of opportunity to learn through classes or shadowing.
Cons
With great power comes great responsibility - because Riot is so open ended, it's easy for people who want clear expectations to find it difficult. You will be given a lot of autonomy, and often expected to make a number of decisions yourself. This openness may also make it uncomfortable when trying to determine priorities on your work - often there is no clear line of decision making, it is up to you to work through those conflicts and set expectations. The lack of clear decision making also gets in the way when trying to gain a commitment for a team to accomplish a goal. In many cases there is no interest in hearing the total cost/investment without already seeing value - so your team may have to develop small chunks and check in to make sure stakeholders still find value in the work.