Preheat the oven to 425F. Line a baking tray with parchment paper.
Add the tomatoes and beans to the tray, and drizzle with olive oil to coat. Season with garlic powder, salt and pepper. Roast for 20 to 25 minutes, or until the tomatoes are blistered.
Meanwhile, in a medium pot over medium-high heat, bring water, milk, and salt to a boil.
Slowly whisk in the polenta, whisking for 3 to 4 minutes. Cover and simmer over low heat for 30 minutes until thickened and the polenta has softened.
Once thick, remove from heat and stir in the black pepper and parmesan cheese.
Divide the polenta into bowls, and top with the roasted tomatoes and beans.