I have played a lot of matches and feel like sharing how I'm feeling about Rosalina's stages, will not be "casual" in any sense except that I will write way less than I could about each stage and will try to get to the essence of what I like/don't like about each. I'm going to include the 14 stages I've seen legal around here; they are in order of preference for me in an abstract match-up (will obviously deviate if I have a match-up or player specific concern). This is from my best stage to worst stage:
Battlefield
Halberd
Skyloft
Delfino Plaza
Kongo Jungle 64
Pokemon Stadium 2
Lylat Cruise
Wuhu Island
Smashville
Castle Siege
Duck Hunt
Town & City
Final Destination
Windy Hill Zone
BF is just an amazing Rosalina stage. She has an extremely good platform game and can control this stage to a generally excessive extent; it's just plain hard to get in on her here if she's smart. I don't really see how it would hurt her in getting juggled; you can use the basic mix-up of land on the platform or not all of the time to get out of juggle situations which is half of why I love platforms with her. That's about it really; it's just all good for her with no real downsides.
Halberd is mostly pretty solid. The shape of the main platform with that one longer low overhead platform is pretty good for her spatial control, and I mostly like low ceilings with her since she mostly kills up (uair/luma jab 3 both kill up, very important when these kill earlier). I feel like sharking is mostly a wash with her; it's something she can do but not particularly better than average so that's neither a pro nor a con. People get scared of hazards here killing Luma; just deploy Luma at the right times if you are scared of that and otherwise enjoy how much control your opponents will often give you for irrational fear of Halberd's non-threatening hazards.
Skyloft is interesting in that I feel like most of the landing zones are kinda bad for Rosalina but the shape of all of the moving sections is fantastic (the one that's the one super long platform especially is very fun!). This stage is so diverse that it tends to be pretty fair in almost every match-up, but Rosalina is a slower paced character so she's pretty good at waiting out the bad and capitalizing on the good so I feel like that diversity is overall a positive for her.
What I said about Skyloft mostly applies to Delfino with Delfino only being slightly worse due to Luma not knowing how to swim so a few landing sites are relatively worse for her than for other characters. It's probably mostly player preference between the two; I like Skyloft more but would definitely understand someone preferring Delfino.
Kongo is funny since the high ceiling is mostly bad but the platform shape is incredible and really enhances her juggle game a lot. The nook in the middle of the stage is funky and is something I like in some match-ups and dislike in others. If you want to play for a timeout or if you're playing someone who kills up better than you, this stage can be a really good pick.
PS2 is kinda the opposite of the true transforming stages; I feel like the default form's platform shape is actually kinda bad for Rosalina, but the transformations are all pretty good. She can control ground's bisected nature pretty well with two characters (either side she's on is just dominated), wind requires her to play carefully but can get her crazy early kills easier than it can give most other characters since it's just a nightmare to be stuck in a very long juggle situation vs Rosalina, electric she can just dominate, and ice is probably about a wash for her but it's so much fun I kinda like it anyway?
Lylat isn't bad. The platform shape is a lot worse than BF but still generally favorable. The ledges aren't a problem; it's not a character thing it's a player thing to have trouble recovering to them so just learn how to do it and enjoy how other players accept a consistent disadvantage for being bad at controlling their recoveries (this advice applies to every smash stage in every game with "bad ledges"; no player maining any character should ever have a problem with them). While this stage is generally too far down on the depth chart to be worth cping for Rosalina, I might actually consider it just because some players are bad with the ledges and might give you free wins by failing to recover.
Wuhu has the general pros for Rosalina as a transforming stage, but the very horizontal layout it usually has just doesn't do her favors and water is also generally not good. I'm not really scared of this stage, but it's honestly only worth counterpicking against someone who is convinced it's a bad stage since they'll play badly here it doesn't do a whole lot for Rosalina herself.
Smashville is a stage I mostly avoid because it's so popular but it's not awful for Rosalina at all. The stage can be kinda cramped at times which is mostly good, and against characters who are bad in the air that moving platform can be very campable (IMO it's more campable than any other platform in the game due to how it moves). It doesn't offer her a lot, but she can work with what's there well enough.
If Castle Siege were always in form 1 it would be a pretty good Rosalina stage. Form 2 is just not one she can practically control and she has no real walk-off game to take advantage of how lengthy that walk-off is around. Form 3 just does very little for her as well; FD with slopes isn't my friend. A lot of players are kinda bad with this stage so if you're confident on all stages it's not so bad, but I'd only consider cping it if I had something super specific read on my opponent about how this one would help me.
All three of Duck Hunt, Town & City, and FD are kinda similar in that they have really limited platform presence which makes stage control harder than it should otherwise be. FD is obviously the worst; I feel like Duck Hunt (poorly placed platforms) versus Town & City (temporary but helpful platforms) is preference and I kinda prefer Duck Hunt (the grass blinds are kinda nice for being sneaky too). None of them are truly "bad", but versus other options, I'd try to avoid all three. Praise for T&C definitely surprises me; I kinda liked the idea of it, but when I played on it more in practice, I found it just generally wasn't helpful and that SV was probably better for the moving platform thing.
Windy Hill Zone is a stage I mostly don't fear because everyone else fears it, but honestly that's all it has going for it for Rosalina. The shape isn't really realistic for her to control at all, and while it's nice how easy it is to kill up, the geography seems to make it a bit harder for her to chase than it would otherwise be. Other characters can get a lot out of the shape and she doesn't; I wouldn't want to come here versus someone actually ready for it at all.
