I assume Roblox supports Windows 10 right now. It’s a relatively stable target of a platform, with various effective anti-cheating defenses. It’s not perfect in that regard, but certainly it ought to be enough for them, so I think it’s a safe bet to say they probably do target Windows 10 today.

Five years from now? I wouldn’t make that assumption, no. They might still support it, but I’m not at all certain of that.