One great 'Red Room Natasha Tony fanfiction' is 'The Red Room's Daughter'. It explores Natasha's past in the Red Room and how Tony might interact with her in that context. It has a lot of action and some really interesting character dynamics.
You can start by looking on fanfiction.net. It has a large collection of fanfictions and you're likely to find quite a few about Tony, Natasha and the Red Room there.
One possible plot could be that Tony Stark discovers the existence of the Red Room and decides to investigate it. He might encounter some of the Black Widows trained there and try to help them break free from the control of the Red Room. He could use his technology to expose the secrets of the Red Room to the world.
One possible reason could be that Tony has some pre - existing biases. Maybe he has a set idea of the type of person he wants on his team and Natasha doesn't fit that mold in his mind. For example, if he's looking for someone with a more technical background and Natasha's skills seem more combat - oriented to him at first glance.
Another theme is teamwork. They are both part of the Avengers, so many fanfictions focus on how they work together on missions, whether it's fighting a new villain or rescuing hostages. Their different skills - Tony's technology and Natasha's espionage abilities - make for interesting team - up scenarios.
Natasha may come to view Tony as a kindred spirit. If she discovers that he also has a longing for real connection like she does, she'll feel a sense of kinship. His true nature might show that he is not as different from her as she initially thought. They could then develop a closer friendship or even something more, as they realize they share common emotional ground beneath their outward appearances.
He might interact with them with a mix of caution and curiosity. Since the Red Room characters are often trained assassins, Tony would be on his guard. But he would also be curious about their skills and how they were trained. He could offer them a way out of the life of an assassin, using his resources and influence.
One common theme is the blending of their two very different personalities. Tony is often portrayed as more flamboyant and tech - savvy, while Natasha is more reserved and stealthy. Their marriage forces them to find common ground and understand each other better.
One common theme is the fear of the unknown. Since they are both superheroes, they're not used to dealing with normal life events like pregnancy. Another theme is the support they give each other. For example, Tony might use his resources to ensure Natasha has the best medical care during pregnancy.
One great 'Tony Stark and Natasha Romanoff fanfiction' is 'The Unlikely Alliance'. It explores their relationship in a post - apocalyptic world where they have to rely on each other's skills to survive. Their banter and the way they gradually come to understand and respect one another is really engaging.