As the title would suggest instead of Riot having to create everything and use their limited resources on select projects. Members of the community with enough skill can take care of task Riot simply does not have time for.
I want to note that I have no idea what kind of repercussions this could lead to nor how implausible it actually is. I just thought it was a good idea for the following reasons.
Free labor: As that would suggest, Riot would only need to make sure people are fully aware that they will not get paid for their efforts, maybe some free RP, but they will not be making a job from this. It is strictly voluntary.
Tedious task: Task that require a lot of work, but are very simple could be given to the community instead. Once the work is complete Riot proof checks it and play test it. If all lights are green it's brought to the PBE then live as normal. That way their developers do not need to waste time on task that are just time consuming.
Potential candidates: Should a community member prove his/her worth by completing a multitude of task efficiently and with great quality. Riot could even offer that person a position should they be willing to accept and circumstances allow.
New perspectives: Perhaps all the members at Riot see something one way, but someone saw it differently that was not in Riot, and that turned out to be the correct solution.
So things the community could work on would be....
Bugs: Trouble shooting, identifying, and fixing bugs. For instance Death Recap and WW have bugs that have lasted far too long. Instead of constantly pushing it to the back burner perhaps give it to the community and state the code must look like X have at it. Should the community successfully fix the problem, it cost Riot nothing, more people are happy, and the game is just more functional. Of course Riot would still need to proof check these codes.
Skins: Community skins are rampant. They are more than qualified to assist. While yes, you do lose some "surprise" factors if you include the community into the skins. You can treat it (hopefully) like play testers and hope they leak no information. This could also include like the effects on Mordes abilities being adjusted to different colors.
Emotes: Like skins the community is more than qualified for this task and could send you millions of high quality emotes that Riot request.
Features: New features like, announcers and finishers, perhaps helping Clash or anything else people can think of, can be developed by the community. If these go in to the game and fail, Riot didn't waste much of their time implementing it.
I think we can see where I'm at with this idea. Just a shower thought that popped into my head. Let me know what you think.
Edit: this image is huge but I love it. How do I scale it down?