Cut the potatoes into very thin, max 5mm thick, slices, then pat-dry them.
Grease a large, shallow baking dish with oil and line it with half of the potatoes. Brush them with oil, then season with salt pepper. Bake for about 10 minutes in a preheated oven (at about 190C degres) until golden, then turn over the potatoes and bake for another 5-8 minutes.
Meanwhile, slice the onion and pepper, chop the rosemary leaves and mince the garlic.
When the potatoes are crispy, lay the onion and pepper slices on top. Scatter the rosemary all over, followed by the the garlic mince.
Add another layer of potatoes and bake for another 10 minutes.
Take the dish out again and turn over the top layer of potatoes. Put the sausages on top of them, season with plenty of pepper and bake for 15-20 minutes or until the sausages are golden brown and the bacon & potatoes are crispy. You might need to turn over the sausages once or twice.
Serve warm.