Preheat the oven to 375°F (190°C). Line 2 baking sheets with parchment paper.
Use a sharp knife to carefully cut a circle around the stem of the pumpkin and remove the top. Use an ice cream scoop to scoop out the pumpkin seeds and flesh of the pumpkin and transfer to a bowl. Set aside.
Cut the pumpkin into large pieces and and transfer to one of the baking sheets. Brush with olive oil and season with salt and pepper to taste. Bake for 1 hour and 15 minutes or until pumpkin is fork tender.
Separate the pumpkin seeds from the flesh and rinse and dry them.
Add the pumpkin seeds to the other baking sheet. Drizzle with olive oil and season with salt and pepper to taste.
Bake for 20 minutes, stirring halfway through, until golden brown and crunchy.
In a food processor, combine the arugula, basil, roasted pumpkin seeds, garlic, olive oil, lemon juice, water, and salt and process until smooth.