Preheat the oven to 350 degrees Fahrenheit.
In a bowl, toss the chickpeas with the oil, chaat masala, garam masala, cayenne or paprika, turmeric, and salt.
Spread the chickpeas in a single layer on a baking sheet.
Place the baking sheet in the oven and let the chickpeas roast 30-45 minutes, until they are crisp. Oven temperatures vary, so if they are not crispy at the end of 45 minutes, give them some more time.
Remove the baking sheet from the oven, place it on a rack and let the chickpeas cool about 10-15 minutes.
Toss the chickpeas with the spring onions, coriander leaves and lemon and sprinkle with some more chaat masala, if you wish. Some people add diced tomatoes, but I prefer not to because they tend to make the chickpeas soggy.