Start by baking the sweet potatoes. Lightly scrub the potatoes and prick with the tines of a fork. Wrap in foil, place on a baking sheet, and roast in a 400 degree F oven until cooked through and entirely tender. The timing will depend on the size of your potatoes, but start at 30 minutes. Once cooked through, remove from the oven, open the foil and allow to rest until cool enough to handle.
To make the topping, in a medium bowl, whisk together flour, sugar, oats, spices, and salt. Add the butter and toss the mixture together with your hands. Break the butter up into the flour mixture until the butter is the size of small pebbles and oat flakes. This took me about 4 minutes. Toss in the coconut and pistachio.
Place an oven rack in the upper third of the oven and set the oven the broil.
Slice the potatoes down the center and press the edges to open the potato a bit. Spoon a heaping 1/3 cup of crumble into each potato. More depending on the size of your potato. Place on a baking sheet and bake until golden and bubbling, about 5 to 7 minutes.
Remove from the oven and serve warm.