Preheat oven to 400 degrees Fahrenheit. Line a large baking tray with parchment paper and set aside.
Sprinkle a large cutting board with a little flour and lay the puff pastry sheet on top. Sprinkle some flour on top of the puff pastry and, using a rolling pin, roll it into a big rectangle.
Spread dijon mustard evenly over the puff pastry.
Next, sprinkle the parmesan and feta cheese evenly over the puff pastry.
Then, layer on sun-dried tomatoes, spinach, green olives, and artichoke hearts.
Roll up the puff pastry tightly into a log and carefully slice it into approximately 1-inch rounds. A serrated knife works best to cut them. Be sure to hold the log securely so that the log doesn't fall apart while cutting.
Carefully transfer the rounds onto the baking sheet in a single layer.
Bake in the oven for approximately 15 minutes, flipping about halfway through. The middle of each round should look just slightly underbaked, but most of the puff pastry should be crispy/flaky and golden brown.
Notes
If you have time, wrap the uncooked pinwheel log in saran wrap and place in the freezer for 30 minutes before slicing the log into rounds. This will make it easier to cut.