Combine first 6 ingredients in a large Dutch oven; bring to a boil. Reduce heat; cover and simmer 20 minutes or until vegetables are tender. Drain. Reserve vegetables and 2 cups cooking liquid; set aside.
Melt butter in a large Dutch oven over low heat; add flour, stirring until smooth. Cook 1 minute, stirring constantly. Gradually add milk; cook over medium heat, stirring constantly, until thickened and bubbly. Stir in pepper. Gradually stir in reserved vegetables and cooking liquid. Continue to cook over medium heat until thoroughly heated.
Ladle soup into individual soup bowls, and serve immediately.