Preheat oven to 400 degrees F.
Line a baking sheet with parchment paper or a silicone baking mat, and place your poblano peppers on the prepared baking sheet. Place in the preheated oven and roast for 25 minutes, flipping the peppers halfway through. They should look blackened and blistered when they are done. If they don't look blackened and blistered, let them roast a few more minutes until they do.
Remove from oven and carefully place the peppers in a bowl. Cover the top of the bowl with a cloth or towel to trap some of the steam in. Let the peppers sit about 20 minutes.
Once peppers are cool enough to handle, remove the stems, seeds, and skins. I like to do this by simply peeling off as much of the blistered skin as I can (it should come off relatively easily), and then removing the seeds and stem by slicing the pepper vertically from top to bottom so that it becomes one long strip. When you do this you should be able to pull the stem and most of the seeds off fairly easily. Wipe off any remaining seeds. Discard the skin, stems, and seeds.
Drain your soaked cashews. Toss the poblano peppers, cashews, garlic, plant milk, lime juice, maple syrup, and salt in a high powered blender. Blend on high until nice and smooth! (This typically takes my vitamix about 90 seconds).
Enjoy your roasted poblano sauce however you please!