Heat olive oil in a large skillet over medium high heat. Add ground beef (and sausage, if using) and cook until browned, about 5-8 minutes, making sure to crumble the beef and sausage as it cooks; drain excess fat.
Stir in garlic and onion. Cook, stirring frequently, until onions have become translucent, about 2-3 minutes.
Place ground beef mixture into a 6-qt slow cooker. Stir in crushed tomatoes (or pasta sauce), diced tomatoes, beef stock, Italian seasoning and basil; season with salt and pepper, to taste.
If you're adding Roasted Vegetables, preheat oven to 450 degrees F. Cut zucchini and eggplant into pieces and place in a bowl. Spray or drizzle with olive oil and toss to cover. Place on parchment paper covered baking sheet. Roast for 15-20 minutes, checking that they don't burn.
Put a whole red bell pepper in a baking dish and put in oven with roasting vegetables. Check regularly, turning as skin turns black. Remove when skin is black and has puffed up. Let cool and remove skin. Cut off flesh and throw away core and seeds.
When the vegetables are roasted, put on cutting board and chop into smaller pieces. Cut up roasted red pepper flesh. Add to meat mixture.
Cover and cook on low heat for 7-8 hours or high heat for 5-6 hours. Uncover and stir in pasta; cover and cook on high heat for an additional 15-30 minutes (check pasta after 15 minutes), or until tender; season with salt and pepper, to taste.
Serve immediately, topped with dollops of ricotta mixture and garnished with parsley, if desired.