Toss the broccoli with the olive oil and spread on a baking sheet. Roast until browned and tender, about 20-25 minutes.
Melt the butter in a Dutch oven over medium heat. Add the flour and green onions and cook for 2 minutes. Add the nutmeg.
Add the potatoes and broth, bring to a boil. Reduce to a simmer, and simmer until potatoes are tender. Add milk and mash the potatoes a bit. Bring to a low simmer.
Stir in the cheese and sour cream, continue cooking until heated through.
Add the roasted broccoli, continue cooking until hot.
Divide into bowls, and top with desired garnishes.