I'm pretty sure the only reason to roast asparagus (other than you need it for your spring dinner situation, and it tastes good, and it's good for you), is so you can make this soup the next day.
So roast a lot while you're at it.
The roasting part is just some asparagus spears on a baking sheet, drizzled with olive oil and sprinkled with salt and pepper, and then let them sort themselves out in the oven at 375 for about 20 minutes. They enjoy a shower of fresh lemon juice before serving.
Save the extras.
Then take some chopped onion. About 1/2 onion for every pound of asparagus. Saute it up in some butter, a couple tablespoons. Add the chopped, saved, roasted, lovely asparagus. Some salt and pepper, and some dried thyme. Move it around til it is soft. Then sprinkle all that with some flour, a couple more tablespoons, and let that mash up a bit. THEN, a splash of white wine, you know what a splash is, and then a couple cups of chicken broth.
Is it simmering and getting thick yet?
Now you add some fresh chopped parsley. Your asparagus should be soft.
Immersion blender. Or regular. Puree the mess of green beauty.
Into that nice mixture, add some heavy cream, maybe a half cup. Test for salt and pepper. And at the very end, because we like full circles and happy endings, squeeze in some fresh lemon juice.
Eat this soup hot or cold.
Be thankful it's spring, even if it is 80 one day and then snows a few days later. We thrive on this personality disorder.