Heat the olive oil in large non-stick frying pan over medium heat, then add potatoes, carrots & rosemary and stir well to coat.
Place a tight-fitting lid on the pan and leave to cook on medium heat for 8 minutes - see my notes for suggestions if your pan doesn't have a lid.
After the 8 minutes is up remove the lid and add sliced sausages, chopped onion and bacon to the same pan and stir well to coat.
Allow everything to fry on medium heat (not covered) for 8-10 minutes (without moving), turning the hash every 2 minutes with a large spatula, (this will give you good colour and caramelisation).
Meanwhile, to make the dressing add all of the dressing ingredients to a small bowl and mix well then set aside.
Once the hash is finished cooking, turn the heat off and then add the dressing to the pan immediately and mix well to coat everything.
Serve with crusty bread.