cooking vegetables for mashing Inspired by some of the answers and comments on a recent question on boiling potatoes whole or diced, I'm curious:

What's the best way to cook a combination of vegetables to be mashed? I'm thinking of a subset of potatoes, turnips, rutabagas, parsnips, carrots, and anything else that sounds good. Obviously if boiling, one wants to avoid waterlogged vegetables, but the cooking times of the various vegetables are different. Is there a reliable way to cook everything together (at least for some subsets)?

Edit: As mentioned in the comment below, I know that the best one can do may be starting with the longest-cooking vegetables and incrementally adding the rest. What I was wondering was things like if some or all were better baked, or if boiling is good, if some besides potatoes are better boiled whole...
After trying steaming a few times as renegade suggested, I've decided I prefer roasting:


As with steaming, everything stays in the vegetables, they're pretty easy to test, and they don't get waterlogged. 
It gives some nice caramelization, contributing a little to the end flavor.
It leaves them drier than steaming, which I like because it gives me the freedom to add plenty of other liquids (e.g. milk).
It's easy to roast large quantities of whole vegetables (which wouldn't fit in anything I have to steam in), so I can make large batches. And cooking them whole means there's less to sort through when pulling out ones that got done faster.


To each their own, but this works for me!