When it comes to asparagus, there are a few different schools of thought on whether or not you should blanch it before roasting. Some people say that blanching helps to retain the bright green color of the asparagus, while others find that it makes the asparagus more tender and easier to eat. Ultimately, the decision of whether or not to blanch your asparagus is up to you and your personal preferences.
If you do decide to blanch your asparagus before roasting, the process is pretty simple. All you need to do is bring a pot of water to a boil and then add your asparagus spears. Cook them for 1-2 minutes until they turn bright green, then remove them from the pot with a slotted spoon and place them in an ice bath. This will stop the cooking process and help preserve their color. Once they're cooled, simply drain them and pat them dry before roasting according to your recipe.
On the other hand, if you choose not to blanch your asparagus before roasting, know that this won't affect its flavor - it will just change its appearance slightly. The asparagus will be darker in color after cooking since it won't have been exposed to boiling water beforehand. Additionally, it may take slightly longer to cook since it won't have been pre-cooked at all. But ultimately, both methods will produce delicious results - so go with whichever one you prefer!