I purchase sandwich or grinder rolls at my local grocery store. I then purchase Hot Italian Sausage grinders in Premo brand. I also purchase onions and green peppers. First you saute the onions and green peppers (sliced) in a pan with butter. Keep a watchful eye on the veggies so as to not brown them too much, unless you prefer them that way.
Next you cook the Premo Hot Italian Sausage in a skillet. Basically add water, the sausage and cover. Heat for 10 minutes, then uncover and heat for another 10-15 minutes. Making sure to turn the sausages as they cook, this ensures each side is browned. I personally hate to mess with raw meat, so I use a meat thermometer to ensure that they temperature of the meat has reached 160 degrees, citing it is fully cooked.
Then place sausage and onions with green peppers in your grinder/sandwich roll. For an added touch to mine, I put a slice of cheese in the bottom of the grinder/sandwich roll first then place sausage and onion and green peppers.