Combine the ground bison and seasonings in a large bowl and mix until well combined.
Scoop the mixture by the heaping tablespoonful and shape into balls. Place on a baking sheet lined with parchment paper and refrigerate while you start the marinara.
To make the marinara, preheat oven to 325°F.
Place the quartered tomatoes, onion, and garlic onto a large baking sheet and toss with the olive oil and salt.
Roast for 35 minutes.
Remove from the oven and transfer everything to a large bowl.
Use an immersion blender to blend until mostly smooth. (Alternatively, you can transfer everything to a blender and blend until mostly smooth.)
While the tomatoes roast, heat the olive oil in a large pan over medium high heat.
Add the meatballs and cook, turning often, until browned on all sides.
Remove the meatballs and set aside. Add the mushrooms, eggplant, and zucchini and sauté until softened and lightly browned.
Return the meatballs to the pan and stir in the marinara. Simmer for about 5 minutes, until everything is bubbly and heated through.