My directions add the roasted veggies to a blender however after the veggies are roasted you could add them to a soup pot along with the coconut milk and broth and use an immersion blender instead of a blender.
For a little chunkier soup pulse it opposed to cranking the blender up on high or what I have done is keep maybe 4-5 of the roasted sweet potatoes out when I first blend the soup. Once the soup is all blended and I have reached my desired consistency I'll add the remaining sweet potatoes in and just pulse the blender a few times so you get some of those yummy sweet potato chunks.
For a more bisque like soup you'll use about 1-1 1/4 cup broth. If you like you're soup thinner use upwards to 2 cups. Start with 1 cup and go from there adding a few tablespoons at a time until you get your desired consistency.
As mentioned in the recipe post I have 2 methods for caramelizing onions. The recipe above suggests roasting them in the oven which is for convenience however you could also caramelize the onions on the stove. If you prefer doing this while the sweet potatoes are roasting heat 1 tablespoon olive oil in a large skillet over medium heat. Add sliced onions to the skillet with a pinch of salt. Cook stirring occasionally until the onions are soft and caramelized, about 15-20 minutes. Once cooked set aside until the soup is ready.
If you like garlic add a few peeled cloves to the sliced onions on the baking sheet too (I do!) The additional garlic cloves is not noted in the recipe about but I usually will add 3-4 cloves to the onions. The garlic cloves will get soft and buttery and is so good!