Your clarification means a lot -- "baked" potato in the U.S. tends to be a whole potato cooked on its own, where the insides become fluffy and creamy, and is done with larger starchy white potatoes, or sweet potatoes work well, too.
Roasted potatoes, on the other hand, tends to be (in the U.S.) be smaller "new" potatoes, waxy potatoes, or even larger starchy potatoes cut up (eg, 'oven fries').
The starchy potatoes only really hold up well when roasting if it's very high heat or a short amount of time -- if you're going to be cooking them with the roast as there's going to be moisture in there, I'd go for a waxy potato (eg, Red Bliss).
As for the browning -- probably coat them well with oil, and if they're not brown enough for your liking when you pull the roast, as you're going to have to rest it anyway, drain the meat juices, crank the oven up to somewhere around 450F (230C) and leave the potatoes in for a few extra minutes.
ps. yes, I know a sweet potato isn't a potato. And I also tend to use Yukon Gold for just about everything, as it makes great baked potatoes, and roasted potatoes (although, not sure how well with a roast at the same time) and they're good in pot roast and stews if you don't add them too early.
Much agreed with Krister that simple is best. Also, to really emphasize the difference, I'd aim for larger flakes of both the 'regular' salt and the sea-salt. Here are some serving ideas.
Just the salt. Side by side, on a dark plate with some small divider. A pinch of each. That's it.
Broth. A very simple vegetable broth, made with a little butter (unsalted of course) and fresh tomato, and perhaps a sprig of fresh thyme or rosemary, warmed to about 160 degrees, and strained through cheesecloth. I'd add about 2/3 the salt during cooking and a few 'fresh' flakes at service.
Fish. Preferably raw. A piece of sushi-grade salmon would be delicious. Add a few flakes of salt.
Meat. Take one very good, very fatty, very juicy piece of meat. Sear it on all sides to about medium rare. Salt.
Chocolate. Salt is a wonderful accompaniment to dark chocolate. And dark chocolate with caramel. Make or purchase such a confection, and serve two side by side with a few flakes of each salt on top.
Fruit. I recommend a piece of watermelon. Possibly grilled. With salt.
Tea. Find a good recipe for salt tea, popular in parts of Asia. Serve in two small Japanese style tea cups.
You have lots of options. Small portions will be key. Not overcooking anything will be key. Interesting options whether or not to tell your guests ahead of a dish which preparation is which, or let them to identify the difference with their palettes. Perhaps a combination, letting them try to guess at first, then with instruction, and finishing with guessing again. I'd add in some history, possibly from the highly recommended book Salt. Or just Wikipedia. Tell them all of the functions salt serves in our bodies, but especially in the transmissions of flavor on the tongue. Great idea...!
Best Answer
Salt that is used for food consumption is always meant to be sodium chloride (and may or may not contain other things such as iodine). Other "salts" (to use the term in the chemistry sense) such as potassium chloride are not generally used by themselves for human consumption or specified in food preparation, even though they are potentially safe to eat.
Sea salt is still 85% sodium chloride but because it has additional chemicals/elements/compounds in it, does have a different taste.
For best results when baking, use plain table salt, sodium chloride, with or without iodine (which is added to provide a necessary nutrient for those not living near a salt-water source of fish or not eating enough salt-water fish). Note from the link that sea salt does not contain enough iodine to supply a nutritionally adequate amount.