Preheat the oven to 425°F (220°C).
In a medium saucepan, combine the rinsed quinoa and 2 cups of water. Bring to a boil over high heat, then reduce to low, cover, and simmer for 15 minutes or until water is absorbed. Remove from heat and let sit covered for 5 minutes, then fluff with a fork.
While the quinoa cooks, place the diced red bell pepper, zucchini, and broccoli florets on a baking sheet. Drizzle with 1 tablespoon olive oil, sprinkle with 1/2 teaspoon salt and 1/4 teaspoon black pepper, and toss to coat evenly. Roast in the preheated oven for 20 minutes, stirring halfway through.
Meanwhile, prepare the chicken breasts by patting them dry. In a small bowl, mix the smoked paprika, garlic powder, 1/2 teaspoon salt, and 1/4 teaspoon black pepper. Rub the spice mixture evenly over both sides of the chicken breasts.
Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add the chicken breasts and cook for 6-7 minutes per side or until the internal temperature reaches 165°F (74°C) and the chicken is no longer pink inside. Remove from heat and let rest for 5 minutes, then slice into strips.
In a small bowl, whisk together the tahini, fresh lemon juice, water, honey, minced garlic, and 1/4 teaspoon salt until smooth. Add more water if needed to reach a pourable consistency.
To assemble the lunch prep bowls, divide the cooked quinoa evenly among 4 meal prep containers. Top each with equal portions of roasted vegetables and sliced chicken.
Drizzle the lemon-tahini dressing over each bowl or pack it separately to add just before eating.
Store the lunch prep bowls in airtight containers in the refrigerator for up to 4 days.