One idea could be that Roy is kidnapped by an old enemy seeking revenge for past deeds. The kidnapper might try to force Roy to reveal secrets about his superhero friends. Another could be that a powerful criminal organization kidnaps him to use his skills for their own evil purposes. For example, they could want him to create special weapons for them.
Another possibility is a new villain who has emerged and sees Roy and Dick as symbols of the superhero establishment that he wants to undermine. This new villain could be someone with a grudge against the way heroes operate in general and thinks that by kidnapping them, he can make a statement.
Roy Harper's fate in the comics is not straightforward. Sometimes he's shown as dead, but comic universes are constantly evolving, and his status can change based on various creative decisions and story developments.
One possible plot twist could be that they were actually set up to be kidnapped by a former ally who has turned against them for some personal vendetta. Maybe this ally blames them for a mission gone wrong in the past and wants to make them suffer.
Fanfiction that involves abuse is highly unethical. In the case of Roy Harper fanfiction, it can be extremely distressing for fans who love the character. It goes against the general positive portrayal and can also promote harmful ideas about abuse, which is unacceptable in a moral society.
Yes, there are. Some might focus on Roy Harper's transformation into a vampire and his struggle to adapt to his new existence. For example, in some fanfictions, he could be trying to resist his newfound bloodlust while still maintaining his relationships with his friends.
The story where Roy battles his own drug addiction is a very powerful one. It shows his struggle not only with the physical addiction but also the mental and emotional turmoil. His journey to overcome it and become a better person is inspiring.