As someone that's worked in trust and safety for a decade. None of this is new nor unique to Roblox, and Robloxs moderation is better than most.
Every single site, game, online space, program, app, etc that has interactive features has both pedophiles and children on it interacting without active monitoring.
It's a fact of the Internet. The best you can do is leverage warn and monitor key phrase lists to take action when conversation veers to the obvious inappropriate line. Nothing anyone can do will ever prevent or stop this interaction.