Heat oven to 425 degrees F.
Place tofu on a plate between two paper towels. Place heavy saute pan on top of tofu and lightly press to remove as much excess moisture as you can. Let sit for 5-10 minutes to drain.
Make the tahini dressing: Whisk together lemon juice, garlic and salt in a medium bowl. Let sit for 1 minute, then slowly whisk in oil, a few drops at a time, until emulsified. Whisk in tahini and enough water (by the teaspoon) to make a thin sauce; taste and add more salt and lemon juice if needed. Set aside.
Slice tofu into 1-inch cubes. Place tofu and broccoli on a rimmed baking sheet, and the eggplant on another. Toss all three items with a drizzle of olive oil and a pinch of salt.
Roast broccoli, tofu, and eggplant for 20 to 30 minutes, until vegetables are browned and tender. Toss vegetables once or twice while roasting.
While vegetables are in the oven, make the quinoa: In a medium saucepan, place quinoa, 2 cups water and ¼ teaspoon salt. Bring to a boil, and then lower to a simmer for 15 minutes, until the grains soften and water is absorbed. Set aside.
In a small bowl, whisk together lemon juice, maple syrup, and remaining ¼ teaspoon salt. After removing vegetables from the oven, toss with the lemon - maple syrup mixture to coat. Add red pepper flakes and mix thoroughly.
To serve, place quinoa in six bowls. Divide roasted broccoli, eggplant, and tofu among the bowls. Add diced tomatoes. Generously drizzle tahini dressing over the bowls and garnish with additional red-pepper flakes, if desired.