Preheat your pan. Set a nonstick or cast-iron skillet over medium heat.
Add a light drizzle of oil and let it heat until it shimmers.
Prepare the sausage. If your square sausage came as a block, slice it into 1/2-inch thick pieces. Pat them dry to help them brown.
Cook the sausage. Lay the slices in the pan without crowding. Cook for 3–4 minutes per side until browned with crispy edges and cooked through.
If the heat’s too high, lower it slightly to avoid burning while the inside finishes.
Toast or warm the bread. Split your rolls and warm them cut-side down in the same pan for 30–60 seconds, or lightly toast your bread. Spread with butter while warm.
Add optional extras. If you’re adding a fried egg, cook it in the pan after the sausage, sunny-side up or over-easy. Melt a cheese slice on the sausage for the last minute if you like.
Assemble. Place the sausage on the bottom half of the roll or toast.
Add your sauce—brown sauce is classic, ketchup works fine, or a mix of both. Layer on extras like egg or onions if using.
Finish and serve. Cap with the top piece of bread. Give it a gentle press, slice in half if you want, and serve hot.