Heat oven to 375°F. In large bowl, mix spinach, chicken, beans, corn, cheese and taco seasoning mix; set aside.
Unroll 1 can of crescent dough; press perforations to seal. Press or roll into 13x9-inch rectangle. Cut rectangle in half lengthwise, then cut crosswise into thirds to make 6 squares.
Spoon about 1/4 cup spinach mixture onto center of each square. Bring up one side of dough over filling and roll up, folding in sides as you roll. Pinch seam to seal. On ungreased cookie sheet, place rolls seam sides down and 2 inches apart. Repeat with second can of dough and remaining spinach mixture. Brush rolls with egg white.
Bake 14 to 18 minutes or until edges are golden brown. Cool 10 minutes. Serve warm with sour cream and salsa.