I'm not sure if there is such a specific fanfiction where a character from Rosario Vampire is reading Naruto fanfiction. Fanfiction can be very diverse, but this seems like a rather unique and specific concept. It's possible that it might exist in the vast realm of fan - created stories, but it would be quite difficult to find without a more targeted search.
One common theme is power combination. For example, Naruto's chakra - based powers combined with the unique abilities of the Rosario + Vampire characters like Tsukune's vampiric powers. Another theme is cultural clash. Naruto comes from a ninja - based culture, and when he enters the Rosario + Vampire world, there are differences in values, social structures, and fighting styles that create interesting scenarios.
A possible plot could be that a powerful artifact in the Rosario Vampire world is being targeted by both Hollows and some rogue vampires. Ichigo and Tsukune find themselves on a quest to protect it. Along the way, they encounter various challenges and meet different characters from both universes. The cultural shock between Ichigo's world of Soul Reapers and Tsukune's world of monsters and humans could also add some comedic and interesting elements to the story.
The combination of different power systems. In Naruto, there are ninjutsu, taijutsu, etc. In Rosario Vampire, there are vampire powers and various youkai abilities. When these are combined in a fanfic, it creates unique and exciting battle scenes.
One great 'Naruto Rosario Vampire crossover fanfic' is 'Naruto: The Vampire Shinobi'. It combines the unique ninja world of Naruto with the supernatural elements of Rosario Vampire in an exciting way. The story follows Naruto as he discovers a hidden part of his heritage related to vampires, and he has to navigate both his ninja duties and this new vampire side.
The plot might involve a threat that endangers both Naruto's world and the world of Rosario Vampire. Naruto, with his Kyuubi - enhanced abilities, teams up with the vampires and other creatures in Rosario Vampire. They'd have to combine their different powers, like Naruto's Rasengan and the vampires' super strength, to fight against the common enemy. It would be a wild mix of ninja action and vampire drama.
Naruto would probably be very curious about the vampires and other creatures in Rosario Vampire. He'd be his usual friendly self, trying to make friends. The vampires might be initially wary of him, especially with the Kyuubi's power, but his positive attitude could win them over. Tsukune, from Rosario Vampire, could learn a lot from Naruto about determination and fighting spirit.
One popular 'naruto rosario vampire crossover fanfiction' might be 'Naruto in the World of Rosario + Vampire'. It often has Naruto's unique abilities and character traits being introduced into the Rosario + Vampire universe, leading to interesting plot developments.
Begin with a prologue that sets up the situation. Maybe there are strange energy readings in both the Bleach world and the Rosario Vampire world that are somehow linked. Ichigo is sent to investigate in his world, and as he gets closer to the source, he is transported to the Rosario Vampire world. Once there, he is greeted by the chaos of the Yokai Academy. You can then start to introduce the different characters and their reactions to Ichigo's sudden appearance. This will slowly build the foundation for the rest of the story.
One idea could be a crossover where Naruto characters end up in the Rosario + Vampire world. For example, Naruto could be mistaken for a powerful yokai due to his chakra. Sakura might study the unique magic in the Rosario + Vampire world. Another could be a vampire in the Naruto world, using their powers in a different way than the normal jutsu.