Preheat the oven to 225C/450F. Slice the bell peppers and onions and arrange on a large baking sheet, sprinkle with 1 tbsp of olive oil, toss and roast in the preheated oven for 20 minutes till slightly charred and cooked all the way through. Take the peppers out of the oven and turn the temperature down to 190C/375F.
Set a large pot of water to boil and cook pasta according to package instructions.
In a large pan heat 1 tbsp of olive oil, then add the Italian sausages with their casings removed, break up the sausage with a spoon and cook till browned, then add the fennel seeds and cook for 30 seconds longer to toast the seeds, pour in the chopped tomatoes, tomato passata and 1 cup/250ml water. (I usually rinse out the tomato can and dump the water into the pan.)
Add in the basil, oregano and a pinch of salt, bring to a boil, then cover with a lid, lower the heat to medium low and simmer for 20 minutes.
Drain the cooked pasta and reserve 1 cup water, add the pasta with the pasta water to the sauce and toss to coat.
Add half of the pasta to a rectangular 9 inch X 13 inch baking dish, then top with a layer of ricotta cheese and a layer of roasted peppers and onions, add the second half of the pasta and top with sliced ball of mozzarella cheese or shredded mozzarella, scatter a few basil leaves all over and finish with a grating of Parmesan cheese all over. Baking in the preheated to 190C/375F oven for 20-23 minutes or until the cheese is bubbly and the pasta is heated through.