Heat oil in large nonstick skillet over medium heat until hot. Add onion and jalapeño pepper; cook 5 to 7 minutes until tender, stirring occasionally. Add roast beef; cook 3 minutes, stirring frequently. Stir in 1/2 cup salsa verde; cook 2 minutes or until heated through, stirring frequently.
Meanwhile, to prepare dipping sauce, combine tomato sauce, remaining 1/4 cup salsa verde, chipotle pepper and lime juice in small sauce pan. Heat over low 5 minutes, stirring occasionally. Keep warm.
Divide beef mixture evenly among slider buns. Close sandwiches. Using panini press or double griddle on medium-high heat, grill sandwiches in batches 5 to 7 minutes until toasted on both sides. Serve sandwiches with warm dipping sauce.
Nutrition information per serving: 408 Calories; 108 kcal Calories from fat; 12 g Total Fat; 3 g Saturated Fat; 4 g Monounsaturated Fat; 46 mg Cholesterol; 684 mg Sodium; 43 g Total Carbohydrate; 3.4 g Dietary Fiber; 32 g Protein; 4.4 mg Iron; 3.4 mg NE Niacin; 0.4 mg Vitamin B6; 1.7 mcg Vitamin B12; 2.7 mg Zinc; 12.5 mcg Selenium; 37.3 mg Choline;