Preheat oven to 400°.
. Grate rind from lemons to equal 1 tablespoon. Cut 1 lemon in half; reserve other lemon for another use. Combine lemon rind and garlic in a small bowl, stirring well.
. Remove and discard giblets and neck from chicken. Trim excess fat. Starting at neck cavity, loosen skin from breast by inserting fingers, gently pushing between skin and meat. Rub garlic mixture under loosened skin. Place 1 sage sprig under skin on each side of breast. Gently press skin to secure. Lift wing tips up and over back; tuck under chicken. Place lemon halves and remaining 4 sage sprigs in cavity. Tie legs together with kitchen string. Place chicken on rack of a broiler pan coated with cooking spray. Sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper. Insert a thermometer into meaty part of thigh, making sure not to touch bone.
. Bake at 400° for 1 hour or until thermometer registers at least 165° or until desired degree of doneness. Transfer to a platter; cover with foil.
. Place a zip-top plastic bag inside a 2-cup glass measure. Pour pan drippings into bag, reserving browned bits in bottom of pan. Let drippings stand 10 minutes (fat will rise to top). Seal bag, and carefully snip off 1 bottom corner. Drain pan drippings from bag into measuring cup, stopping before fat layer reaches opening. Reserve 1 tablespoon fat; discard remaining fat.
. Add enough broth to drippings to equal 1 1/4 cups; add reserved 1 tablespoon fat and flour, stirring with a whisk until smooth. Pour broth mixture into broiler pan. Cook over medium heat 5 minutes or until thick, scraping pan to loosen browned bits. Remove from heat; stir in remaining 1/4 teaspoon salt, remaining 1/4 teaspoon pepper, and minced sage.
. Remove and discard lemon and sage from cavity of chicken. Carefully remove and discard skin from chicken and sage sprigs from breast, reserving garlic mixture. Spread garlic mixture over chicken. Cut chicken into quarters. Serve chicken with sauce.