I actually love playing that MU a lot, perhaps because one of my favorite rivals I've ever had is Sethlon. I think it's evenish (to the point where I don't really care who wins) but it can be a struggle in neutral.
https://www.youtube.com/watch?v=Z4WhGfyNroQ
The key to the matchup is to understand exactly what Roy's range is and which attacks he's likely to do. Playing Roy a little and getting a feel for what attacks you'd like to do in various situations can help.
Against U-air strings, SDI them upwards. A lot of people try to DI sideways but this only extends them. The same can be true for Fairs; SDI them away so you take as little damage as possible.
You want to have a solid understanding of how to combo Roy; the classic U-Throw -> U-Air -> Bite combo works on Roy's fallspeed class and is a crowd favorite as well (:3). Wario CCs a lot of Roy's moves well, but don't get overzealous in holding down; one of Roy's best options is Grab and his other moves will cause tumble, leading to a tech-chase.