Rinse the sole fillets, pat dry and roll up with the skin side facing inward. Secure with toothpicks. Season with salt and pepper and saute lightly in olive oil on all sides. Place in a parchment paper-lined, ovenproof dish and bake in an oven preheated to 70°C (approximately 150°F) top and bottom heat for about 10 minutes. Remove from oven.
Pour the balsamic vinegar and stock in a saucepan and let boil down while stirring. Rinse, trim and remove any hard stems from the arugula leaves and season with salt and pepper.
Place the sauce and arugula on warm plates and place the fish rolls on top (remove toothpicks). Serve garnished with cilantro and lemon zest.