Which of the LARGE beef roasts are the tenderest, without going as high as tenderloin, etc.?

Inside round or whole round this is what many caterers use for large crowds also the whole hip was used on cruise ships thus the term steamship round , it was nice and large and provides for rare near the bone medium and well done on each roast . The whole hip though requires a commercial oven or a large spit

Brisket can be roasted. And if you roast it slow it is sooo tender and good!

http://recipes.kaboose.com/fabulous-slow-roasted-b...

Any cut of beef that's fairly marbled (chuck is good too) is really good for slow roasting. That's assuming you have the time to roast them most of a day. You can do them a day ahead of time and then reheat in the oven, I believe. Just keep them in their juices and reheat slowly so they don't get dry. Or just add some kind of sauce or gravy.

flank steak. slow roast it and cut against the grain. Serve with a nice sauce...I prefer horseradish sauce personally

If you can't do prime rib or a Chateaubriand, then you're probably looking at Top round.

chuck roast. they are HUGE