In a saucepan of actively boiling lightly salted water, blanch the potatoes for 8 to 10 minutes, or until the tines of a fork will just pierce the surface. Drain and, when cool enough to handle, cut them in half and score the cut side of each with the tines of a fork. Preheat the oven to 375 degrees an heat a large cast-iron skillet over medium heat. In a bowl, combine the potatoes with the olive oil, oregano, salt, and pepper and toss together until evenly coated. Transfer the potatoes to the hot skillet and spread them out into an even layer so they are hardly touching each other. Heat until sizzling, then transfer the skillet to the hot oven. Toast, turning over every 10 minutes, for about 30 minutes, until very crisp and golden.
While the potatoes are roasting, heat a large non-stick skillet over medium-high heat and add 2 tablespoons water. Cook the sausages for about 20 minutes, turning occasionally and pouring off the fat as it accumulates. Drain the sausages briefly on a double thickness of paper towels and slice them 3/4 thick. Place a slice of sausage on top of each roasted potato half and secure with a toothpick. Assemble the hors d'oeuvres on a platter and squeeze a little lime juice over them. Serve, accompanied by Avocado Salsa