Mix ground beef and sausage into a large mixing bowl. (When it comes to ground meat, using your hands is honestly the best way to mix well!)
In a separate small bowl, combine all the remaining ingredients EXCEPT for the eggs. Mix thoroughly.
Add contents of the small bowl into the large mixing bowl. Mix well.
Add eggs and continue to mix, and don't be afraid to use your hands.
Roll mixture into meatballs, about two tablespoons each, and place at the bottom of your slow cooker.
In a medium sized mixing bowl, combine all tomato sauce ingredients together and mix well.
Pour tomato sauce on top of meatballs in the slow cooker.
Cook on high for 4 hours or on low for 8 hours. (My slow cooker cooks a little too quickly, so if yours is like mine, then I'd cut the time down to 3.5 hours on high and 6-7 hours on low.
Serve over pasta, zucchini noodles, spaghetti squash, or a salad!