In a large bowl toss cauliflower with enough olive oil to lightly coat all the pieces then spread them out in a single layer on a rimmed baking sheet.
Place cauliflower in a preheated 425 degree oven and roast, turning pieces occasionally until almost tender (between 20-30 minutes)
Remove cauliflower pieces to a bowl with tongs; set aside. There should be some olive oil left on the baking sheet. Very carefully pour the leftover oil into a soup pot or dutch oven.
Add minced garlic to the oil in the pot and sauté over medium heat until just golden.
Add cauliflower, artichoke hearts and vegetable stock to the pot and bring to a boil. Turn heat way down and simmer for a few minutes until cauliflower is fully tender (check with fork).
Remove pot from heat and let cool slightly. Puree the soup until smooth using a food processor, blender, or immersion blender. Return to pot.
Gently reheat soup then add one cup of light cream, zest of one lemon (not juice), crushed thyme, and lots of salt and fresh ground pepper to taste. Soup can be thinned with extra broth or water if desired. Remove from heat when soup is heated through again.