Raven Roth may also be a character who has a mysterious past related to the dark arts. Maybe she was once involved with a group or a situation that had ties to Voldemort, but she has now turned against the dark side. Her knowledge of the dark arts, though dangerous, could be used to help Harry Potter understand his enemies better and find ways to defeat them. This complex backstory would make her a very interesting character in the fanfiction.
I'm not sure who Randy Roth specifically is without more context. There could be many people named Randy Roth. He could be an ordinary individual, a local figure in a certain community, or perhaps someone known in a specific field like business, arts or sports.
The uniqueness of their relationship. Tam and Sheldon are both very different characters. Sheldon is extremely intelligent but socially awkward, while Tam has his own set of qualities. Fanfictions that explore how they interact and complement each other are special. For example, Tam could help Sheldon in social situations that he struggles with, like understanding group dynamics at school.
Since I haven't read the fanfic, it's hard to say exactly who Raven Roth is. But based on the title, Raven Roth is the one who breaks Naruto's heart, so could be a character created for this particular fanfic.
Perhaps an intelligent and patient psychologist. She could help Sheldon understand his emotions better. Given Sheldon's complex personality, she would need to be very understanding and be able to handle his idiosyncrasies. This type of girlfriend could also introduce Sheldon to the world of human emotions in a more systematic way.
One great Young Sheldon Tam and Sheldon fanfiction could be one where Tam helps Sheldon with a difficult science project at school. Tam might bring in some unique ideas from his own background that Sheldon hadn't considered. Another could be a story about their friendship growing over shared interests in comic books, despite their different personalities.