Seed and chop 3 peppers. Stir together chopped pepper, next 4 ingredients, and 1/4 teaspoon salt.
Butterfly roast by making a lengthwise cut down center of 1 flat side, cutting to within 1/2 inch of bottom. From bottom of cut, slice horizontally to 1/2 inch from left side; repeat procedure to right side. Open roast, and place between 2 sheets of heavy-duty plastic wrap; flatten to 1/2-inch thickness using a meat mallet or rolling pin. Spread pepper mixture over roast. Roll up, and tie at 1-inch intervals with string. Place, seam side down, in a lightly greased 11- x 7-inch baking dish; cover and chill 8 hours.
Seed and chop remaining 2 to 3 jalapeño peppers. Stir together peppers, butter, and remaining 1 teaspoon salt.
Grill pork, covered with grill lid, over medium-high heat (350° to 400°) 40 minutes or until a meat thermometer inserted into thickest portion registers 160°, turning and basting often with butter mixture. Slice and serve with gourmet greens.