I know that in New Super Mario Brothers Wii, if you had the super guide even show up you were screwed over for a special-looking save file (I think it sparkled). It's purely cosmetic, but I'd really like to know if anything like that happens in here or Nintendo listened to the players and made that only happen if you actually used Rosalind's guide.

No, I don't think so. I only had Rosalina show up once though (didn't use her), but even then, my save file was sparkling after completing the final challenge, as well as a platinum crown. Maybe someone else knows. But so far, I think it's all the same, whether the guide shows up, and whether you use her or not.