I watched a video a while back about this, but the details are fuzzy. I think it was the one I linked below if you want to look more into it. In essence, there aren't a ton of cases where kids are actually being forced to work. However, there are strong incentives for kids to work on Roblox projects that the developers themselves push. The devs want a constant stream of content and money coming in, but they don't want to pay adult workers at adult wages, so they offer Robux to players who make games. It is difficult for people to convert Robux to actual cash, and the money they receive is often significantly less than they would if they put the effort into any other form of work, so many of these kids are essentially making content for the developers for free or significantly less than they should earn. If there was no payout for content creators and the kids were doing that development just because they had passion for the game, it might be a different situation, but there are quite a few kids that believe they can make serious money doing this and don't understand that the developers are exploiting them and paying very little. Adults can probably do more research and better understand the situation they are getting into, but kids often don't have the same critical thinking skills as adults and will accept the lie being pushed by the developers and community that they can get rich by contributing to the game they love.

Video: https://youtu.be/_gXlauRB1EQ

Follow-up: https://youtu.be/vTMF6xEiAaY

The details are too much to go into here in a simple comment. For a full investigation into Roblox check out this video by People Make Games, a games journalism site:

https://www.youtube.com/watch?v=_gXlauRB1EQ

Essentially, Roox makes billions off the free labour of children. The entire eco system is set up to funnel kids into a cycle of consuming others content and producing their own. It's also completely unregulated which has allowed some shady people, some of whom are, or directly work for, the owners of the platform to set up quasi developer studios where children are subjected to the same appealing treatment and exploitation of the regular games industry, while earning none of the revenue.