In a large pot heat olive oil over medium heat. Add sausages and brown on all sides until cooked through, about 10 minutes. Drain grease and set the sausages aside.
Slice sausages into bite-sized pieces.
Add marinara sauce, sliced sausages, onion powder, garlic powder, and Italian seasoning to the pot and simmer on medium-low heat. Add ½ cup of water to the marinara jar and shake to get any remaining sauce out.
Bring a large pot of salted water to a boil and cook spaghetti to al dente according to package instructions. Reserve 1 cup of pasta water and drain noodles.
Toss pasta with sauce, thinning with pasta water as needed. Serve topped with Parmesan cheese.
Notes
Keep leftovers in an airtight container in the refrigerator for 4 days.