best way to reheat roasted vegetables

They're good at room temp, but unless you've roasted them into oblivion the first time, it's fine to reheat them in the oven - a good do-ahead dish, not precise or fussy. Ideally, I'd reheat quickly at 400-ish, but I often reheat them with whatever else is in the oven at 350 or so.

Make the best vegetable soup you ever had by adding them to your favorite stock. Keep it chunky, or process if you prefer.

I like eating them room temp once they have been fully cooked. Otherwise, you may end up with mushy vegetables. You could also use them as is in a pasta, rice, quinoa or green salad.

Depends on the veg. But I would just "re-roast" them. Back in the oven, high heat (400/425-ish) until hot and "roasty" again.