Match your dish to a texture goal: mash needs creamy-dry, roast needs tender-starchy, casserole needs hold.
Use the ratio from the list: yam and squash are closest at 1:1, pumpkin often needs ¾:1 to avoid extra moisture.
Prep for even cooking: cut into 1-inch chunks (or thinner if roasting fast) so everything finishes at once.
Adjust sweetness and moisture: if the substitute is wetter (pumpkin), reduce added liquids; if it’s less sweet (russet/carrot), add a small sweetener and spices.
Taste and finish: for mashes, blend until smooth; for roasts, salt well and roast until browned edges develop.