Poke holes in the sweet potatoes with the tines of a fork. Roast sweet potatoes for 30 minutes, directly on the oven rack or on a baking sheet until soft and cooked through.
Meanwhile, while sweet potatoes are roasting, prepare the crumble: Add oats to a blender. Blend on high until a coarse oat flour is created. Add to a bowl. Add pecans, 1/8 teaspoon salt, 1/4 cup honey, and 1/2 tablespoon oil and stir. Reduce heat to 375 degrees (when the casserole is assembled, the dish will go back into the oven). Allow sweet potatoes to cool.
When cool enough to handle, peel the sweet potatoes, discard the skins, and put the potatoes in a bowl. Add milk, vanilla, 1/8 teaspoon salt, and 2 tablespoons honey to sweet potatoes. Mash.
Put the mashed sweet potatoes in an 8 x 8-inch baking dish or a casserole dish. Add the crumble in an even layer on top. Bake in oven for about 15-20 minutes until the crumble has hardened and browned on top. Enjoy!