Preheat the oven to 425°F. Slice the sausage, bell peppers, and onion and spread them on a sheet pan.
Sprinkle sausage mixture with one teaspoon Creole seasoning, minced garlic, and olive oil. Toss the sausage and vegetables too evenly coat everything with the seasonings and oil.
Bake for 10 minutes, until the sausage is starting to sizzle and the vegetables are beginning to soften.
Meanwhile, prepare the rice (I used Boil-in-Bag rice and followed the microwave instructions).
Stir tomato paste and the other teaspoon of Creole seasoning into the rice.
After the sausage and peppers/onion has cooked, add the tomato seasoned rice, the shrimp, and the tomatoes to the pan and stir well.
Put the pan back into the oven for 3-5 minutes, just until the whole dish is warmed through. (If you are using raw shrimp, you want them to turn from blue/grey to pink and opaque; this should only take 3-5 minutes as well.)
Remove sheet pan from oven.
Squeeze the lemon juice over the jambalaya and drizzle with a couple tablespoons of melted butter, if desired.
Serve immediately, garnished with sliced green onions.