I think the first two members may be overexaggerating about the matchup. It's bad, don't get me wrong, but it's not as bad as you two are saying. Rosalina has the range, she has stage control, and it's really difficult to close in on her, and being the close quarters character that we are, that is really not a good thing. Fireballs are essentially useless in this matchup because of her down b and her pesky luma being her bodyguard. So baiting out shields with fireballs is a meaningless tactic unless you find the right opportunity. If you try to bait out her down b to take the fireball, it won't work because that fireball surrounds her for a short time, making approaching pointless.This means that our approach is limited to down b and running in, where the former is very easy to punish, especially with the range that rosalina has.It's hard to juggle her as well considering how light she is and the fact her air mobility is pretty good. Luma being able to hit from a distance gives us trouble while we're recovering, and on stage when we're trying to approach. I also find that her uair and usmash kill us a lot earlier than most chars, which is very annoying.
However, once you get the two separated, GO FOR LUMA FIRST. Trust me this is a good decision, because once luma is off the field, rosalina loses all the range and tricks she had and has to rely on her slow speed to get a good solid hit and approach. The luma is gone for about 8 seconds, which should give you enough time to rack up damage and/or go for a kill. These 8 seconds are crucial to dish out as much as you can on her. If luma is there and you get a grab, don't always go for the dthrow approach, because luma can punish you after you've completed the throw, making follow ups hard. Go for a pummel or a back throw so that luma gets hit in the process. This way, you are able to get some damage and possibly get her offstage. Down throw is good if luma is farther away/dead. Our attacks also kill her earlier, so if you get a nice read, a bair or an upsmash will get the job done; a good up b read is also great because of how early it kills and how easy it is to hit rosa's fatass with it. Gimping her recovery is tough, though, but it can be done by going for a dair spike while she is rising (she'll mostly rise in a curve to throw you off).
I also want to point out that since custom moves are legal in some tournies, she most likely will use the teleporting luma custom, making her already good range even better as she can basically teleport the luma to a spot where you will be and punish with a smash or aerials. However, our custom 2 down b (mach cyclone) kills luma extremely early if you manage to hit it with the final hit of the custom cyclone, which makes it very easy to go after rosalina. However this also takes away the regular down b approach, which might make it tougher to get in. But recovery is ten times easier this way. Luigi's custom 3 side b (quick missle) makes his recovery phenomenal, and its a lot harder to punish him when hes sliding on stage so fast, especially with rosalina, who has a pretty slow ground game. I'd recommend using this down b and side b for this matchup (if your tourny allows custom moves). Bouncing fireball (neutral b custom 2) seems to be a better option too as it allows for a good edgeguard mixup (throw fireball as she's recovering, and finish with a dair), as well as a good offstage mixup in general, especially when regular fireballs are nothing to rosalina. It can also serve to hit rosalina while avoiding luma as it falls in an arc.
I don't know, I still think ZSS is a harder matchup. I can agree on 65-35 or 70-30 Rosa
