Update: Aside from Roll, I'm also trying to improve some Robot Master sprites.
*And I found some built-in bad sprite coding. Take for example Bubbleman:

Take note on Bubbleman's top, its misplaced (this is also present in the JP version). Also his official art has him with a green vest.
His sprites doesn't have any, just a green jewel on his chest. I added the vest as seen in the pic.
*Did anyone notice why Sparkman's face is black? It appears that only his eyes & open mouth were skin colored.

Then I tried putting his face on the black area of his face. He is surprisingly a good-looker.

*I had an issue with Crystalman's color of him being green. His official art of has him in light-blue:

Now Crystalman is now light-blue. Alas, his Stage Select portrait still has him in green. Oh well.
I would check Napalmman's color. He's supposed to be purple, but his sprite is blue.
Chargeman has red & orange, but his sprite is orange & white.
Now I should go back to Roll-chan 2. But seeing that most of the US versions of MM3-MM6 have their title logos compressed.
Maybe I'll try & work out a US Titlescreen logo for "ROLL-CHAN".