Preheat your oven to 425F degrees. Cover a large sheet pan with foil, making sure it goes up and over the sides.
Take a medium microwave-safe bowl and place a very wet dishtowel in the bottom.
Put the potatoes in the bowl, and cover with the edges of the towel and microwave for 4 minutes.
Meanwhile, slice the top and bottom off of the beets. Using a sharp knife, slice down the sides to remove the skin. Cut into quarters and add to a large mixing bowl.
Add the rest of the veggies, onion, and garlic. Drizzle with 2 tbsp olive oil and 2 tbsp of Everything But The Bagel seasoning. Mix to combine.
Carefully remove the potatoes and place on a large sheet pan. Use a large spoon or the bottom of the bowl to gently press down on the potatoes to flatten them. Sprinkle with a pinch of kosher salt.
Add the veggies to the pan. Bake for 12 minutes.
Meanwhile, slice the chicken sausage and toss with 1 tbsp olive oil and 1 tbsp of the seasoning.
Add the sausage to the sheet pan if there is enough room, or another pan if necessary. Bake until it has reached your desired crispiness (~15 more minutes).
Notes
Use fully-cooked sausage.If possible, divide the mixture onto two sheet pans to help everything cook evenly.Homemade Bagel Seasoning:1 part sesame seeds, 1 part dried onions, 1 part dried diced garlic, 1 part poppy seeds, 1/2 part kosher salt, 1/2 part black sesame seeds.