Preheat the oven to 400°
In a deep saute pan over medium high heat, add sausage links and ½ inch of water. Cover with a lid and allow sausage to simmer in water for 10-12 minutes to cook through.
Meanwhile, slice peppers and onion into long strips. In a separate saute pan, cook over medium heat until soft and slightly browned, 5-10 minutes
Remove lid from the sausage and drain water and cook an additional 5 minutes to brown.
On a baking sheet lined with parchment paper, split open hoagie rolls. Place one link in each roll. Top each sausage with ¼ of the onion pepper mixture, ¼ cup of marinara, and ½ cup of cheese.
Bake in the oven for 10 minutes or until the cheese is melted and browned. Serve immediately.
