Using a heavy bottom pan, add the vegetable stock, cover and heat on high until boiling.
While you are waiting for the polenta to boil, clean and chop the zucchini, yellow squash and quarter the mushrooms. Place on a cookie sheet. Drizzle with olive oil and sprinkle with salt & pepper. Place in the oven & roast for 20 minutes total, stirring once at the 10 minute mark.
Add the marinara to a small pan over medium low heat - stir occasionally.
When the stock begins to boil, add 1 teaspoon salt and 2 tablespoons butter. Set your timer to 25 minutes and while the stock is at a full roiling boil, slowly sprinkle in the polenta, whisking briskly the entire time. Continue whisking and the polenta will begin to thicken. Reduce heat to medium low and whisk the polenta every 4-5 minutes. You may need to add additional water. You'll want the polenta to be about the consistency of a thick pancake batter or thick stew. A couple minutes before it's done, stir in the ricotta and polenta cheese and the remaining butter. Heat thru. Serve topped with roasted vegetable and a dollop of red sauce.