Roblox is not the predator. There's a learning opportunity for discernment here, if you child is mature enough for that lesson. If he's not, well, play with him to the extent you have the time.

Dark alleys at 3 AM in inner cities aren't the predator either. The Everglades swamp isn't the predator either.

One good strategy to avoid being preyed upon is to avoid places where the risk of predators is unacceptably high.

Roblox is also a predator. They are exploiting children for money, through the user generated content and marketplaces. They take an incredibly large cut from everything sold and then have crazy high thresholds before you can cash out. Roblox might not be sexual predators, but they are predators.