Heat oil in a large stock pot over medium-high heat. Add sausage, and cook, stirring to crumble, about 7 minutes or until sausage is done. Remove sausage with a slotted spoon and drain on a paper towel-lined plate.
Add onion, carrots, and celery to drippings in pan, and reduce heat to medium. Sauté vegetables 5 minutes or until tender. Add garlic and rosemary, and cook 30 seconds longer.
Add chicken broth, tomatoes, 2 cans of beans, and the sausage stirring to combine. Bring to a boil. Reduce heat and simmer 10 minutes. Meanwhile, mash remaining beans with a fork.
Stir mashed beans and kale into soup, and cool 10 minutes longer or until kale is tender.