Mander..
with Jimmy Dean it's likely to be sage. If I remember correctly it's a very sage flavored sausage. It's also quite fatty so having a larger ratio of fat in it might help too. I don't know what recipes are out there for the copy cat Jimmy Dean, but I make my own sausage at times and can also suggest either letting it sit for 24 hours once you have mixed it together to gt the best flavor.
I have made apple, maple, honey roast, itatlian etc. all the same way. I started out making them because I was using ground turkey as a healthy option.