Preheat your oven to 400°F or 200°C (400°F).
In a large 3-quart rectangular baking dish, combine the eggplant, red onion, and sweet peppers.
Drizzle with 1 tablespoon (15 ml / 0.5 fl oz) of olive oil and sprinkle with salt, tossing gently to coat everything evenly.
Roast for 30 to 35 minutes, stirring twice, until the vegetables are tender and starting to brown at the edges.
While the vegetables are roasting, prepare the sauce.
In a small saucepan, heat the remaining 1 teaspoon (5 ml / 0.2 fl oz) of olive oil over medium heat.
Add the minced garlic, dried thyme, crushed fennel seeds, black pepper, and crushed red pepper.
Cook and stir for 2 minutes until fragrant.
Stir the condensed tomato bisque and water into the saucepan.
Bring the mixture to a boil, then reduce the heat. Allow it to simmer, uncovered, for 5 minutes, stirring occasionally to prevent sticking.
Meanwhile, cook the pasta according to package directions until al dente.
Drain well and return the pasta to the hot pot.
Add the roasted vegetables, the prepared tomato sauce, and the fresh baby spinach to the pasta, stirring gently until the spinach wilts and everything is well combined.
Transfer the entire pasta mixture back into the baking dish you used for the vegetables.
Sprinkle the shredded mozzarella cheese evenly over the top.
Bake, uncovered, for 15 to 20 minutes, or until the sauce is bubbly and the cheese is perfectly melted and golden.
Don't overcrowd the pan when roasting vegetables. Use a large baking sheet if needed to ensure they roast and brown, rather than steam.
Let the pasta bake rest for 5-10 minutes after removing it from the oven. This allows it to set up, making it much easier to serve.
