Preheat oven to 425°; chop cauliflower into 1-inch pieces, spread on a sheet pan, drizzle with 2 tbsp oil + season with salt/pep; roast 10 min, then flip veggies over + roast 5-10 min more until browned + tender

Meanwhile, dice onion; heat 1 tsbp oil in medium pot over med-high; sauté onion 3-5 min until tender

Peel + dice both potatoes; add 3-4 cups water, seasoning packet + potatoes to onion; bring to a boil + cook 12 -15 min until potatoes are tender

Add cauliflower to soup; in batches puree soup until smooth; return soup to pot, taste + season with salt/pep; divide to bowls