Ended up waiting too long, and having my thoughts of the matchup already said by various other people. So in order to beat the buzzer, I'm just going to throw random matchup tips in no particular order. I will say however that unless you're going for a timeout, you need to be comfortable being aggressive with Rosalina.
- Generally, if you want to use her down special, short hop it. It allows you to carry a bit of momentum if you want to use it as an approach, or retreating option, and a Luma aerial ( generally the quick nair ) near the ground will make it safer, as well as catching any metal blades you might have sucked in. I don't see a reason not to do it this way every time.
- I've had moderate success using RAR Gravitational Pull into LL Luma Back air on a projectile read. You give yourself the projectile immunity, and the special priority of Luma back air should beat, or at least tie with the Megaman's down tilt or dash attack, which still leaves you in an advantageous position ( close to Megaman ).
- Get good with items, and know the tech associated with them. Gravitational pull isn't an excuse to ignore item tech. With Rosalina, Luma, and a Metal blade, the character's combo potential rises quite a bit, while denying Megaman a projectile option. Experiment with z-drop mixups ( sometimes catching it again with an aerial, sometimes dropping with it for a grab ). Keep in mind that most Megamen will try and destroy the metal blade with their jabs, so anticipate the option and plan accordingly.
- Without customs, sending Luma out is awful. I'd recommend keeping the meat shield as close as possible, and try to squeeze as much value from its lifetimes before it inevitably dies to lemons, or Megaman's other quick options.
- Know gravitational pull has a deadzone, where if Megaman is close enough, you're going to be hit regardless. This is most important when avoiding his up air. If you expect the opponent to close the distance, treat it as any other deadly up air, air dodge, or try and knock him out of the startup with one of your own aerials.
- Up tilt is disturbingly good out of shield. I've been up tilt punished by simply poking a shield with down tilt, which is a shockingly high punish for one of her quickest options. A Megaman who knows how to use this move on reaction wins the guaranteed kill department by a long shot. Your best bet is try and bait the move ( very carefully ), and punish the enormous amount of lag it has. A whiffed up tilt has enough delay that you should be able to take your pick of smash attacks, and even charge it for a bit.
- In terms of edgeguarding him, she has a fairly easy time hitting him if he goes low with her everlastingly long nair, followed by a down air once he has no option but to up b immediately. Going high isn't terribly good for him either. Despite his aerials usually beating Rosalina's, you're free to punish them if they land on a platform, or otherwise trap their landing.
Oh and 50-50 is probably right, so mark me down for that.