I too cut my pork loin so that I can lay it flat only to be rolled up later. As for stuffing?
I make/or buy cornbread and crumble it up. I then sauté onions celery and carrots with some salt and pepper. Once these start to soften up I add chopped dried dates and cranberries. After a few minutes of sautéing I add some chicken stock and let it reduce. I the. Add my crumbled cornbread and mix it all together. I usually make my stuffing in advance and allow it to cool completely before I stuff my pork loin.
Spread stuffing onto pork loin as evenly as possible and roll up. I try to keep the fat part of the loin up top. I then wrap in bacon an sprinkle with my favorite dry rub. Smoke till temp hits 150.
22.5" WSM, 22.5" Weber Kettle, Kenmore 6 burner Gas Grill.....Where's The Beef?