In my opinion, a tier list should be a visual representation of who has the best matchup spread, scaled with the meta -- getting scraped by sheik is much more meaningful than being 9:1 vs Pacman.
Using these parameters. Rosa is not top 3. She loses hard to ZSS, Sheik, Pikachu, Falcon, and perhaps others. Yes, she is very good. She is a noob killer with amazing options, frame traps, etc. She's great. However, because her bad matchup are what you encounter at tournaments.
Still not on a proper keyboard, so this is the short version, but, yeah, Rosa is top 5. She can't be top 3 when other characters have better spreads vs the meta.