Identify your use: roasting, soup, or mash/puree—then pick the substitute that matches the texture you need.
Substitute 1:1 by weight for the squash-for-squash options; for the carrot+potato mix, use the listed blend ratio.
If the substitute is watery (frozen squash or blended mash), drain and reheat briefly to thicken before seasoning.
Adjust flavor: for milder options (delicata), add a little salt and a pinch of nutmeg or cinnamon to bring back warmth.
Taste and fine-tune your final texture: blend smooth for puree, or roast longer for firmer edges.