You can't ever "crisp up" frozen vegetables, but you can roast them. They don't carmelize in the same way, and they do have a softer texture than fresh. My two favorite ways to make frozen veggies are
Open frozen bag, splash in a little olive or walnut oil, and seasonings (sometimes ranch dressing powder, or may favorite teriyaki sauce) and shake in the bag, and roast at 375 to 400.
or add frozen veggies to a bowl, and add favorite vinaigrette dressing. Cover bowl and refrigerate alllowing veggies to marinate and thaw. I also like to add a couple of the following before or after thawing, doesn't matter: diced onion, olives, canned or pickled mushrooms, pickled yellow pepper rings, artichoke hearts (canned, frozen or pickled), canned beets, canned or pickled baby corn.