Place the roasted vegetables (tomatoes, garlic cloves and onions) in the blender along with any of its juices released during roasting. You can add a little water to help it blend.
In a large pot on medium heat, add butter and all purpose flour. Using a WHISK, mix for around 30-45 seconds (to get the flour slightly toasted and get rid of its raw smell).
Gradually add the water while whisking to prevent any lumps from forming.
Increase the heat to medium-high heat.
Add in the blended vegetables.
Add salt (1 teaspoon for now), black pepper powder, oregano, paprika powder, and sugar.
Bring to a boil and let it boil for 20-25 minutes.
Turn off the heat. Add in the baking soda and stir.
Taste and adjust the seasoning (especially the salt).
Optional step: Add cream into the soup or drizzle on top while serving.
Add mint or basil on top.
Serve with croutons or crackers.