Roll is said to be remarkably bad in Marvel vs. Capcom 2. Even in a game where Dan Hibiki and Servbot exist as fighters, Roll is still regarded as the absolute worst character. Some would even go so far as to say that Roll is the most garbage character in all of fighting game history (of those that are competitive).
Jmcrofts recently released a video that has him overviewing what makes Roll so bad in Marvel vs. Capcom 2. Towards the end of the video, he also played some matches against one of the greatest Marvel vs. Capcom 2 players ever, PG|Justin Wong — with Justin Wong using Roll.
Roll’s ability to absorb damage in Marvel vs. Capcom 2 is straight up awful. She’s tied with Akuma, Servbot and Wolverine (Bone) for heaving the least amount of damage resistance.
All characters have 143 points of health in Marvel vs. Capcom 2, but every character is able to reduce damage based on their defense. While the Sentinel takes 25% less damage from attacks, Roll takes an additional 38% damage when she takes a hit.
Being a very small character, Roll is also incredibly stubby. Combined with her weak damage output, she really struggles at winning battles of attrition. Still, her projectile is actually fairly decent, though it’s said to be a worse version of Mega Man’s.
Roll actually does have a few redeeming qualities as she gets a double jump and an instant overhead. Jmcrofts also notes that her supers are at least usable.
When Justin Wong uses Roll, he’s able to reliably pressure Jmcrofts with her thanks to Doctor Doom’s rock assist. Funnily enough, this actually says a lot about how strong Dr. Doom’s rock assist is seeing as how it can even make Roll seem like a decent character.