Experience Ratings

The Experience Ratings feature is a feature that was first introduced to Roblox experiences on June 18th, 2013. Verified users can rate experiences they have visited by giving them a "thumbs up" or "thumbs down". This was made to nudge the Discover page closer to Roblox's vision with "a [Discover] page that's loaded with fantastic [experiences] to [visit] and worlds to explore." This feature is mandatory and cannot be disabled by experience creators. The rating system is known to be similar to YouTube's own rating system.

Moderation
Ratings are monitored by the Roblox Staff. If any experience in particular is massively down-voted, the staff will investigate the activity to make sure it's not malicious in nature (such as a single user creating alts to dislike an experience).

Criticism
Around late 2014, popular users such as were targeted by rating botters. Voxhall ended up getting terminated and never unbanned. This caused an outrage on the forums as rating botters could do the same to almost anyone. The same day, other users have ended up getting terminated from the botter, some losing millions of value.

Future Plans
The Experience Ratings feature is planned to be integrated into the Discover page (but not as a sort). Experiences that are overwhelmed with "thumbs down" votes would be pushed down the Discover page, and eventually off the Discover page entirely, even if it is being visited frequently. Additionally, there are plans to expand this feature to all assets on the site.

ESRB feature
In July 2020 it was announced on Twitter that the ESRB features will be added in the future.

Blog Post
http://blog.roblox.com/2013/06/thumbs-up-to-game-ratings/