Heat oven to 425°F or 400°F convection bake with the rack in the middle.
On a rimmed baking sheet, toss the broccolini with olive oil and Magic Mushroom Powder. (If you don’t have Magic Mushroom Powder, you can use 1 teaspoon of Diamond Crystal kosher salt or ½ teaspoon Morton’s kosher salt/fine grain salt).
Arrange the broccolini in a single layer on the rimmed baking sheet.
Grab the sausage and roll out some meatballs! (If the sausage is in links, just pierce the casing with a knife to get to release the meat inside.) Scoop out uniform-size balls with a medium disher and roll out about 24 meatballs that are about 1½ inches in diameter.
Tuck the meatballs in any open spots between the broccolini on the baking sheet.
Pop the baking sheet in the oven. Roast the sheet pan meatballs and broccolini for a total of 15 to 20 minutes or until the meatballs are cooked through and the broccolini is charred in places. Rotate the tray 180° at the 8 to 10 minute mark to ensure even cooking.
While the sheet pan supper is cooking, heat up the marinara sauce in a saucepan on the stovetop or in a glass container in the microwave oven.
When the sheet pan meatball supper is ready, take it out of the oven and spoon on the marinara sauce!