Pre-heat the oven to 425°F.
In a roasting pan, coat the potatoes, carrots, parsnips and celery root in just enough EVOO to coat, then season with salt, pepper and nutmeg. Roast the vegetables until tender and caramelized at the edges, about 40-45 minutes.
Puree the vegetables in batches with the garlic and stock and transfer to a soup pot. Season the soup with honey and hot sauce, to taste. Cool and store for make-ahead meal.
To reheat, reheat in a soup pot over medium heat.
To make the cheese croutons, on the night you want to serve the soup, pre-heat the oven.
Arrange a cooling rack over a baking sheet and assemble two cheese sandwiches using two bread slices and two slices cheese per sandwich. Cube each sandwich into nine mini-sandwiches and separate onto a baking sheet, providing space between each mini-sandwich. Coat the sides and tops of each sandwich with cooking spray. Bake in the hot oven until golden and the cheese melts. Float a few sandwich-croutons in each bowl of the soup bowls.