For the cannelloni baked in the oven, you need to first prepare 400-500 ml of besciamella sauce (add into the sauce 100 g of grated parmigiana cheese for extra creaminess), then prepare a relatively dry/stiff ground beef (400g) and tomato sauce (passata di pomodoro, 700g) with mirepoix. For the mirepoix I normally fry in EVOO two finely chopped carrots, one big finely chopped red onion, 1 cup of minced parsley and/or basil, and 2 finely chopped celery stalks.
You need also 2 mozzarellas on top of the stuffed pasta tubes. Stuff the tubes with ground beef & tomato sauce. Btw, you do not need piping bags or spoons to fill in the tubes, but simply press repeatedly the uncooked cannelloni tubes against the thick sauce and cannellonis will self-fill themselves; if that makes any sense. After filling and layering the tubes on to an oven tray, sprinkle over the cannelloni tubes shredded mozzarella and more parmiggiano cheese, if you like. Then pour over the besciamella sauce, and bake in 180 Celsius convection oven until golden brown (approx. 30 minutes).