I have roasted frozen vegetables. There's no need to defrost them -- just thrown into the oven frozen. They have to be cooked longer, but you can definitely do it. Don't expect the same results as fresh -- but let's face it, that's true for all frozen vs. fresh vegetables. I also cook a lot of frozen veggies in the winter & like the variety roasting can provide.

About thawing them first (do not place in water) and then braise them with some oil/butter or pancetta and some garlic over the stove. Or...

Frozen veggies are usually blanched before freezing, so I would think that trying to roast them would not work so well, because of the additional water content. If you decide to try, we'd love to hear if it works or not, and I wouldn't roast them frozen. I'd let them thaw at room temp or overnight in the fridge, and pat them as dry as I could. I also wouldn't thaw them under running water for fear of adding even more moisture to the party.

raquelita, i have never tried to roast frozen vegetables, but i have heard mixed reviews. some people find success (especially with brussel sprouts, it seems like) and other people turn out with a wet and mushy mess. my advice would be to stuck to seasonal vegetables for roasting (root vegetables in the winter are excellent roasted and very under-appreciated) but if you want to try the frozen ones, you will likely have to do trial and error to figure out what works best for you. if you decide not to defrost them first, many people just give them extra time until they turn that lovely golden brown color on the outside, but i would worry that the outside would cook while the inside remains frozen. I would suggest defrosting them submerged in water so they defrost gently and the vegetable cells don't get destroyed from thawing them too fast. i hope this helps!