1. Center a rack in oven and heat to 375 degrees. Unroll both cans of dough and separate into individual triangles. On a cookie sheet, arrange triangles to form a ring with pointed ends facing outward and bases overlapping, leaving a 4" space empty in center (dough should resemble a starburst shape). Press firmly on overlapping dough to seal.
2. Spread cream cheese over dough, leaving top 1" of pointed ends bare. In a large bowl, combine spinach, mozzarella, salt, and garlic powder and mix with hands until spinach is broken up and ingredients are evenly distributed. Spoon filling onto overlapping parts of dough to form a ring, then sprinkle evenly with pimientos.
3. Working with one triangle at a time, pull pointed end toward center and tuck underneath base to enclose filling; repeat with remaining triangles to form a wreath (some filling will still be visible). Brush top and sides of dough with beaten egg and sprinkle evenly with Parmesan.
4. Bake until deeply golden brown, 25 to 30 minutes, rotating halfway through. Carefully slide a metal spatula underneath wreath to release dough from pan, then slide onto a platter and serve warm.