Using kitchen shears, remove the backbone from each hen. Press the center of the breast with the heel of your hand until you hear a pop and the hen lies flat.
Season both sides of each hens generously with salt and place them on the baking sheet. Arrange the veg around the hens. Place the baking sheet in the oven and roast for 20 minutes.
Place the butter, pecans, brown sugar, and soy sauce in a small saucepan. Stir until the mixture comes to a boil. Stir in the Dijon mustard. Spoon over the hens and the veg until evenly coated.
Scatter the pecans evenly across the baking sheet and return to the oven. Roast for an additional 15 minutes or until the hens are golden and the juices run clear.
Tent the tray in foil and let rest for 10 minutes. Transfer the veg to a platter. Arrange the hen pieces on top of the veg.