Coat a small nonstick skillet with cooking spray; add margarine. Place over medium-high heat until margarine melts. Add mushrooms and green onions; saute 2 minutes. Add cheese, minced marjoram, and pepper; cook, stirring constantly, until cheese melts. Remove from heat; add crabmeat, breadcrumbs, and lemon juice, and stir well.
Spoon crabmeat mixture evenly onto fillets; roll up each fillet, jellyroll fashion, beginning at narrow end. Secure with wooden picks. Place rolls, seam side down, in a small baking dish coated with cooking spray. Bake, uncovered, at 350° for 10 minutes. Sprinkle Swiss cheese over rolls; bake an additional 10 minutes or until fish flakes easily when tested with a fork. Remove wooden picks, and, if desired, garnish with lemon wedges and marjoram sprigs.