My 12 year old is obsessed with Roblox and it's making me nervous

He's not just playing it, he's watching YouTube videos about Roblox, joining Discord servers about Roblox, spending his allowance on Robux. I'm worried about predators and also about how much he's into it. I get the appeal of online gaming with friends but this feels different. I asked to join a server with him once and he was embarrassed which made me more concerned. Tried talking to his mom about it but she thinks I'm being overprotective. Is this normal for his age or should I be worried? Any other dads dealing with this?