Okay, I will make my post since @
Luco
kindly directed me to this.
(Skip first paragraph if you don't care about my introduction)
I will introduce myself. I am Kodystri. As many people on Smash Ladder knows, I am usually on the top of SmashLadder until I started sandbagging with Lucas(Mainly because of experience), but I am mainly a Ness main and use him for majority of tournaments. Most people would call me a "Wi-Fi Warrior." or something similar like that. Not only I am that, I am also a rising player in Georgia, a region filled with amazing Rosalinas such as @
Neos and @
Gadiel_VaStar . True, they may not be amazing as Dabuzs, but they are still amazing Rosalinas regardless in my eyes. I am currently ranked 23rd in Georgia's PR, although I have started beating PR players in Georgia as of lately.
Without further delay, lets get to the MU.
I feel like the MU is +2 in Rosalinas favor and both customs and default.. I highly believe this is Ness's worst MU follow closely by Sheik, Mega Man and Sonic(the Ness boards will strike you to the ground that Sonic is THE worst MU *pokes*). Besides the gimps, Ness really struggles in the neutral game. I know in the past I have advertised that Ness won the neutral game on a reddit post, but as more Rosalinas got more advanced and perfected this play, I no longer believe this.
Why does Ness not win the Neutral Game? Because Luma. I like to occasionally joke that Luma is the character and Rosalina as the sidekick, but it is especially true in this MU. Ness has an incredibly hard time dealing with Luma. All of Ness's aerials doesn't knock away Luma until Luma is at low enough health and Ness's aerials are extremely important, PK Thunder gets absorbed by Magnet, and PK Fire just straight up misses Luma unless its in the air.
So what knocks Luma away? His Aerials when Luma has less than half its health, PK Thunder, Smashes, and Dash Attack. PK Thunder is unreliable because Rosalina can absorb it, Smashes require hard read or puts you in a long frame duration(Down Smash can miss too), and Dash attacks sends Luma straight up, and you need the Luma to go off the stage instead. So in other words, Ness can't really get rid of Luma without putting tons of effort while many other characters can get rid of Luma much more reliably such as Mario, Sonic, Lucas, and Captain Falcon's dash attack.
Whats even worse, Ness has an INCREDIBLY hard time landing vs Rosalina and Luma, especially on platform stages like Battlefield and Dreamland. Because Ness is really floaty, Rosalina can Up Smash or Up Air Ness for days. Many times I have lost 40-100% because I wasn't able to land and the Rosalina was predicting my landing correctly. Ness just can't really do much about it besides either grab the edge, or outpredict her. Grabbing the edge is risky because if Rosalina and Luma knocks you away before grabbing the edge, say goodbye to your stock. Rosalinas, i am telling you, abuse Ness's bad landing options.
In the Neutral game, Ness basically just has to punish while Rosalina can just dance on him all day. PK Fire is almost useless in this MU as Rosalina's Run and Dash Attack goes over that move. PK Thunder, an important juggling tool, is useless against Rosalina as she can just Gravitational Pull it. Ness's aerials, although one of the best aerials in the game, have short range aside from Fair, which does only 8% and staling just makes that aerial worse. Ness's Fair and Uair beats Rosalina's Nair, but loses to her Back Air, and maybe Fair iirc unless spaced perfectly. Rosalina's aerials have great Range where as Ness's does not have the best range. What makes this worse is Rosalina is one of the hardest characters to grab, and Ness's momentum comes from grabs(although he does not rely on this and Ness mains can do fine without it). Regardless, this almost invalidates a kill option unless the Rosalina just screws up horribly. Even if Ness gets the grab, he can only UThrow, Fthrow, or BThrow because Luma makes Down Throw combos impossible. Rosa's needs to get Ness in the air to make the MU much more easier.
Now to the infamous gimps. Rosalina gimps Ness hilariously easy. Tbh, I don't even think she needs Gravitational Pull to gimp Ness as her Down Air is extremely disjointed and would gimp Ness regardless. Gravitational Pull just makes it effortless and easy to do. Basically, if Ness has to recover with PK Thunder, Ness is dead unless the Rosalina didn't feel like going out there. What the Ness can do is recover early and high or recover far enough away to grab the edge from that point as Ness has invincibility during part of the duration of PK Thunder. If you recover high with PK Thunder, you will probably eat an Up Air, Forward Smash, Up Smash, or Down Smash(The most optimal punish imo as it sets you up for a gimp). Lets just say that Ness almost has no hope in recovering if he used his second jump.
After reading all of this, you are probably wondering I haven't really given advantages to Ness at all. That is because he really only has three. Edgeguarding and Strong Punish Game and speed in his moves. Those are the only two advantages he has in this MU. You may be laughing that Ness can edgeguard Rosalina, but definitely no harder than edgeguarding Pits. Rosalina does not have a hitbox aside a while after free fall as Luma can do something. Ness can do his normal edgeguarding tools except PK Thunder as Rosalina invalidates it. However, you can bait Rosalina into doing that and take a hard punish with Bair or Uair. If you are a Ness main and you are going to win this MU, you better edgeguard Rosalina as this is your only advantage. If you screw up the edgeguarding by edgeguarding with an aerial.... well... lets just say gg stock. And if Rosalina is on the edge trying to get back on, Ness can cover most of these options, but he has to commit to one of the other. Down Smash covers the Get Up, Attack, Jump off the stage, and Jump but fails to get the Roll unless it was used to early. Down Smash really only gets Get up and Attack in most cases and sometimes can get Jump and Jump off the stage if you are frame perfect. Also Rosalina has to recover low or Down Smash can end Rosalina's stock fairly early, but she also risks being stage spiked by Fair or Nair.
Now to Ness's Punishes. Ness, punishes SUPER hard. Rosalina may win the MU, but you better not screw up or Rosalina may lose a potential stock. This is especially true as Rosalina is the 5th Lightest character in the game. Rosalina can't afford being hit by PKT2 or a Tipper Bat as those hits like a truck and have amazing knockback. And even though it is hard to land, Back Throw can end Rosalina's stock earlier than most characters, so you definitely have to respect that. Also, you have to be reminded, all of Ness's aerials aside from Dair kills pretty early. Nair kills around 140% while Uair kills around 110%(And even earlier with rage!) Back Air kills stupidly early near the edge and Fair can kill and difficult to tech if using it to stage spike.
Ness does have speed in his moves, that is the last advantage he has in this MU, but Rosalina's huge hitboxes and disjointed hitboxes basically makes this part ineffective.
Well, this is all I have to say about MU. I may be extremely bias as I hate fighting her(I main her in every other game that features Rosalina because I love the character, and I would probably be a Rosalina main if it wasn't for Ness, but regardless, i still respect Rosalina mains) and generally do better with Mario, Lucas, and Lucina, my secondaries than I ever due with Ness, which is practically only true in the Rosalina MU and the Mega Man MU.
I was rating this a -3 for Ness, but I did take it as a -2 even though I still believe it is a -3.
So Outcome?
With Customs +2 in Rosalina's Favor
Without Customs +2 in Rosalina's Favor