Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper.
Heat a large skillet over medium-high heat. Add the sausage, breaking it into small crumbles with a wooden spoon as it cooks. Cook until browned and no longer pink, about 5-7 minutes. Transfer to a paper towel-lined plate to drain excess fat.
In the same skillet, add 1 tablespoon of olive oil if needed (depending on how much fat the sausage rendered). Add the sliced onions and cook over medium heat until softened and beginning to caramelize, about 5-7 minutes.
Add the minced garlic and chopped sage to the onions. Cook for another 30 seconds until fragrant. Remove from heat.
Roll out the pizza dough or crescent roll sheet onto the prepared baking sheet. If using crescent roll dough, gently press the perforations together to seal them.
Brush the dough with the remaining tablespoon of olive oil. Sprinkle with a pinch of salt and black pepper.
Spread the onion and sage mixture evenly over the dough, leaving a 1/2-inch border around the edges.
Distribute the cooked sausage crumbles over the onion mixture.
In a bowl, combine the mozzarella, fontina, and half of the Parmesan cheese. Sprinkle this cheese mixture evenly over the sausage.
Drizzle the honey lightly over the top and sprinkle with red pepper flakes if using.
Bake for 15-20 minutes until the crust is golden brown and the cheese is bubbly and lightly browned.
Remove from the oven and sprinkle with the remaining Parmesan cheese and fresh arugula if using.
Let cool for 2-3 minutes before slicing. Serve warm.