Moai is THE villain. I heard most of Japan also just hates how he plays and how disrespectful he is sometimes. I haven't met him in person so I don't want to spread myths that he's rude or anything.
Type-Lumina is an exceptionally balanced game overall. You might think it's quibbling, but people say there's an S-tier and then there's an A+, A, and A- tier, then below that there's Neco Arc... but even Neco Arc, a joke character, made it shockingly far into the Evo brackets. It's simply that every character has good tools which allow them to win. But it's true that, within this compact tier list, Roa is one of the best characters, even if his advantage isn't enormous relative to other games. His gameplan is extremely solid, consistent, and he can just force it on you. It's not necessarily the most overpowering one available (Aoko, Vlov, PCiel, Arc, Warc, and DAN are all nuts, but they're just the most obvious ones to mention) and he's not really the greatest in any single area, but he doesn't really fail in any crucial area either, so he has no especially notable weaknesses. Consider his neutral: there are other characters who are better at zoning _in general,_ but his 214 and 236 specials are fast and able to counter more dedicated zoners while still being able to effectively lock down non-zoner characters (particularly through the highly spammable 214C). This is his most notable quality, but he also has excellent pressure and strike-throw mix-up and got big damage after being blessed with j.2C, which also helped out his air game (the one place he's rather lacking). He's a great character and everyone knows it, but he's not really busted or stupid compared to any of the others. What Meltan players say is "Roa is fumble-proof," which makes him reliable during tournaments. I think what it comes down to in this case is that Moai really is just that good. Still, I wouldn't be surprised to see Roa nerfed next patch cycle, either indirectly through changes to basic system mechanics which presently favor him somewhat, or curtailing his damage a bit.
I wish Evo and other major FG contests had a random select category for every game repped. No more top-tier spam! Variety and the chance to see how elite players fare with underused characters!