There is also a big difference between "work" and "potentially earn robux through playing Roblox". If you are making your 10 year old sit at a desk all day doing Roblox development - I agree, that's bad, that's child labor, that should be stopped. If your 10 year old has used the Roblox editor suites to create his own game and hopes to earn robux with it - that seems like a fine use of time.

There is a girl in my neighborhood who is constantly making and selling things door to door. I've bought a bracelet, cookies, and slime from her. Is this wrong? She's probably 10-12 years old and, I assume, earning less than minimum wage. Should I call the police? Child protective services? Do we need a law to stop her from doing this?

I would say that it isn't wrong for children to do things like this. It's behavior driven by the child that isn't harmful and might be beneficial. Why should you want to stop that? Same logic applies to Roblox.