Preheat the oven to 425°F (220°C).
Cut the pumpkin into small cubes and remove the seeds. Place the pumpkin cubes on a baking sheet lined with parchment paper and drizzle with olive oil. Season with salt and pepper to taste. Toss to coat.
Roast the pumpkin in the preheated oven for 25-30 minutes, or until tender and lightly browned. Allow to cool.
In a small bowl, whisk together the olive oil, balsamic vinegar, dijon mustard, salt, and pepper to make the dressing.
In a large serving bowl, combine the mixed greens, roasted pumpkin cubes, pumpkin seeds, and crumbled feta cheese. Drizzle with the dressing and toss to coat evenly.
Serve the roasted pumpkin salad immediately and enjoy!