Prepare barbecue (medium heat).
Sauté Soyrizo in large skillet over medium-high heat until cooked through, breaking up with spoon and set aside, about 8 minutes.
Mix 2 1/2 cups watercress and goat cheese in medium bowl.
Lightly brush 1 side of each pita bread with oil.
Grill, oiled side down, until bottom is just crisp, about 2 minutes.
Transfer to work surface, grilled side up. Cover each pita bread with cheese mixture, Soyrizo, and several sweet pepper rings, dividing equally.
Return pita pizzas to barbecue. Grill, covered, until goat cheese softens, about 2 minutes.
Transfer pita pizzas to serving platter.
Top each with more watercress and serve.