Depending on the sausage you start with, you can stuff fatties with almost anything! Cheese, other meats, peppers, onions, etc. I have a friend that starts with bulk Italian sausage flattened out and stuffs it with prosciutto, mozzarella cheese, fresh spinach, roasted pepper and onions, then rolls it up. Very good!
I'm getting hungry from just looking at that. Sadly, I have no ingredients to make one this morning. My FIL who is an ex-marine has some saying about piss poor planning.
Anyhow, I find that fatties can be stuffed with anything. Most frequently, I lean towards onions, portabellas, peppers, and cheese. I keep telling myself to add eggs to it. Frankly, there's always so many other ingredients, I make the eggs on the side.
RD Turned me on to stuffing fatties with more than just cheese. This one was done with Shallots, baby bellas, garlic and some other stuff that I cannot remember at this time. I use a caramelized onion and roasted red pepper sausage. These fatties are packed w/flavor. Haven't tried RD's roll method though.
Larry W. your buddies fatty sounds great, I wonder how some fresh basil in there would be?