For vinegared rice: wash rice under cold running water, rubbing grains together with fingers, till water runs clear. Drain. Combine rice, cold water, and salt in a medium sauce pan; bring to boiling. Reduce heat, cover, and simmer 15 minutes or till liquid is absorbed. Remove from heat; stir in vinegar, sugar and sake. Cover and cool to room temperature. If using green beans, cover and cook with carrot in a small amount of boiling water for 10 minutes or till vegetables are just tender. Drain and cool. For each omelet roll, beat 1 egg with 1 tablespoon water. Pour into a lightly greased 8" skillet with flared sides; lift and tilt the skillet to spread evenly. Cook over medium heat 1.5-2 minutes or till set. Omelet may start to brown. Do not turn. Remove from the pan; cool. Trim cooled omelet using a sharp knife to cut away two of its opposite curved edges so it resembles a rectangle. Roll up tightly, jelly-roll style, beginning from a straight edge. To toast seaweed place each sheet on a broiler pan and broil 5-6" from the heat for a few seconds or till color changes to a lighter green. Broil one side only. To assemble spread 1/2 cup vinegared rice over each seaweed sheet, spreading to within 1" of one edge and to the other three edges. Center 3-4 salmon strips, an omelet roll and/or vegetables on rice atop each seaweed sheet. Select filling ingredients as desired. Starting opposite the side that has rice spread to within 1" of the edge, roll up each sheet jelly-roll style. Press the seaweed edge lightly to seal. Slice each roll crosswise into 3 pieces; cut each piece in half diagonally. Place, diagonally, cut side up, on serving plate. Makes 36 pieces.