With a small paring knife, cut off the bottom tip of each sprout. This will release the outermost leaves; put leaves in a large mixing bowl. Continue to trim a thin slice more off the bottom stem, teasing each layer of leaves off, and adding them to the bowl. Stop when you have removed all the leaves and you are left with the heart or core of the sprout. (Save cores to roast later if you like.)
When you have removed all leaves you can, toss the leaves gently with the oil, sprinkle ever so lightly with salt. (Really, do NOT have a heavy hand with the salt because the salty flavor intensifies with roasting. Just sift a few grains between your thumb and forefinger.) Lay leaves in one layer on a rimmed baking sheet. The leaves, during tossing, will want to cup together, so take care to remove them from nesting together as you arrange them on the baking sheet. They need to toast in one layer for best results.
Roast for 10-15 minutes, until leaves are lightly browned and crisp. The wide variation in time is because of the differences between home ovens. Check at 10 minutes, and remove any that you think are done, putting the rest back in for another minute or 2; check again and remove those that are done. You don't want the entire leaf to be fully toasted or it will be too bitter. You'll get the hang of it and your oven's peculiarities after the first batch.