Add the cut potatoes and onions to a large bowl. Add 2 tablespoons olive oil, garlic powder, salt, rosemary, thyme and black pepper to the potatoes and onions. Stir gently using a rubber spatula or wooden spoon to combine and coat with the seasonings.
Brush a sheet pan with 1 tablespoon of oil.
Arrange sausages on the sheet pan.
Arrange the potatoes and onion mixture around the sausages.
Bake the Italian sausages for 20 minutes.
Turn each sausage so that the paler side is now up.
Bake for another 15-20 minutes or until the sausages are a golden-brown color.
Test if the sausage is done with an instant read thermometer. Take the temperature of a couple of links, specifically, one in the middle of the pan and one that’s along the edge. Make sure the internal temperature is at least 160°F; if it’s not, continue cooking for 5-10 minutes and check again.