Preheat the oven to 425 degrees. Grease two baking sheets with nonstick cooking spray. Set aside.
Measure the water into a Pyrex measuring cup or other microwave-safe container. Microwave on high for one minute 10 seconds.
While the water is heating, add the hot roll mix to a large mixing bowl. Combine the flour mixture and yeast packet. Add the olive oil, and give the mixture a couple of stirs.
Add the water to the roll mix. Bright the mixture together with a large wooden spoon until it's cool enough to handle.
Transfer the dough to a pastry slab or other large work surface dusted with flour. Knead it for 2-3 minutes, adding flour as needed.
On a floured surface, divide the dough into eight equal portions. Allow it to rise, uncovered, for 10 minutes.
While the dough is rising, make the calzone filling. Spray a large frying pan with nonstick cooking spray. Break the sausage into chunks. Turn the heat to medium. Cook the sausage, breaking into smaller pieces as it cooks. Drain the meat thoroughly.
While the meat is cooking, add the shredded cheese and thawed spinach to a medium-sized mixing bowl. Combine thoroughly.
When the meat has finished cooking, add it to the cheese and spinach. Combine thoroughly.
On a floured surface, roll out a ball of dough. Add a 1/2 cup of filling to one side of the dough. Fold it over, pinching the edges. Place the newly formed calzone on one of the baking sheets. Repeat this process for the remaining calzones.
Bake for 12-13 minutes, rotating the pans halfway through.
Allow to cool for five minutes before serving.