Preheat your oven to 375°F (190°C). Turn on your convection fan if you have one.
Melt the butter in a small pan over medium heat. Add the garlic, jalapeños, cumin seeds, fennel seeds and coriander seeds. Stir for a minute or two, until the spices are lightly toasted. Remove from the heat and stir in the curry powder, ginger and salt.
In a large bowl, combine the butternut squash, cauliflower and apples. Add the spice mixture and toss together until everything is evenly combined. Transfer the works to a 13- x 9-inch (3 L) baking or roasting pan, spread it into an even layer and roast until the vegetables are tender and lightly browned, about 1 hour.
Just before serving, stir in and top with the chopped cilantro.