Rub butternut squash with 1/2 T oil and sprinkle with salt and pepper on a large baking sheet. Place in oven and roast for about 10 minutes.
After squash have baked for 10 minutes, add mushrooms to same pan as squash (or a separate pan if there isn't room), rub with 1/2 T oil and place pan back in oven for about 15 minutes until squash and mushrooms are fully cooked.
Heat 1/2 Tbsp. oil in a large saucepan over medium heat. Add onion and sauté for 2-3 minutes to soften. Add garlic and cook for another minute.
Add rice to pan with onion and garlic and stir for 2-3 minutes. Add white wine to rice and stir until mostly absorbed.
Ladle 1/2 cup broth into pan with rice and stir until mostly absorbed. Continue adding broth half a cup at a time, stirring continuously. Repeat adding more broth every few minutes when rice has absorbed most of liquid (takes 20-30 minutes total).
Add spinach and sage to rice and stir 1 minute until spinach is wilted.
Remove from heat and add mushrooms, butternut squash, toasted walnuts, nutmeg, and parmesan. Season with salt and pepper and serve immediately.
* If using regular, non-sprouted brown rice, you'll need to par-boil first. To do this, bring a medium pot of water to a boil with approximately 1 tsp. salt and add rice. Boil rice for 15 minutes (do not cover). Remove rice from heat and drain water using strainer. Complete the rest of the recipe as directed but only use 4 cups of broth instead of 6.* Toast nuts by placing on a baking sheet in the preheated oven for about 5-6 minutes or stovetop by toasting in a dry pan over low-medium heat.