Preheat the oven to 300 degrees. In a large bowl, gently toss the oats, pistachios, coconut chips, olive oil, agave, egg white, salt, cinnamon, three tablespoons of the rose petals and the rose water (if using), until evenly coated. Transfer the granola to a large rimmed baking sheet and spread in an even layer. Bake for about 35 minutes, stirring every 10 minutes, until toasted and golden brown; rotate the sheet halfway through baking.
Let the granola cool completely, then sprinkle the remaining rose petals over the top; toss gently. Store in an airtight container at room temperature for up to one week.