Peel the onions and garlic, and quarter the onion and cut into ½-inch pieces. Remove the stems and seeds from the peppers and cut in half lengthwise.
Place the tomatoes, peppers, onions and garlic on a roasting pan. Drizzle with olive oil and sprinkle with salt.
Preheat your grill, smoker, or oven to 450 degrees and roast for about 20 minutes. Flip the tomatoes and veggies over and roast for an additional 15-20 minutes.
Remove the tomatoes and veggies to a sauce pot or Dutch oven and add in about a tablespoon of olive oil. Sauté for about 5 minutes over medium heat.
Add in the remaining sauce ingredients and stir to combine. Bring to a boil, then reduce to a simmer, and simmer for about 30 minutes.
Allow to cool slightly then blend until smooth with an immersion blender or in a food processor or blender. Return the sauce to the saucepan, cover, and heat over a low simmer to keep warm.
Grill the Italian sausage on your grill or in a skillet until the reach an internal temperature of 160 degrees, then remove to a cutting board and cut into slices.
If desired, cut some additional onion and bell peppers into ½-inch pieces and sauté in oil until soft.
Cook your desired pasta, following package instructions, until al dente.
Gently stir together the pasta, sauce, grilled sausage, and peppers and onions. Serve warm and top with shredded parmesan cheese and fresh basil.