Preheat oven to 425°; chop cauliflower into 1-inch pieces; wipe mushrooms with damp paper towel, remove stems + scoop out gills, then slice; spread veggies on a sheet pan, drizzle with 3 tbsp oil + season with salt/pep; roast 10 min, flip + roast 5-10 min more til browned + tender

Meanwhile, microwave 2 sweet potatoes in their wrappers on high, 6-8 min, flipping halfway through; scoop flesh out of the skin + into a bowl; mash using a fork + season with salt/pep; divide to bowls

Heat skillet over med-high + warm grains with 1 tbsp water for 2 min, stirring occasionally; divide to bowls

Top bowls with roasted veggies + ½ butter to each