In a large kettle or Dutch oven, saute the celery, onion, garlic and rosemary in butter until tender. Add the broth, peas and salt if desired; bring to a boil. Reduce heat; cover and simmer for 1-1/2 hours or until peas are soft. Remove from the heat and allow to cool.
For meatballs, combine the pork, rosemary and pepper. Shape into 1/2-in. balls. In a large skillet, brown meatballs until no pink remains, about 5 minutes.
Ladle half of the cooled soup into a blender or food processor; puree. Return soup to the kettle along with the meatballs and heat through.