Help with Roast Beef for Sandwiches
Top sirloin roast (aka top butt, top sirloin butt, center-cut roast, or spoon roast) is well-marbled and meaty-flavored. It is a cheaper cut. One recommended method is to determine what you want the final temperature of the meat to be, then to set the oven to that temp (or as low as it will go if it's lowest setting is higher than you want) and slowly roast until it reaches the desired temp. This method yields even done-ness throughout the roast. If you want a brown crust you can pan-sear first but the meat won't then be as evenly cooked.
You're probably gonna get plenty of conflicting (or perhaps differing) opinions. I think flavor-wise, one of the best cuts is well-marbled, boneless ribeye. However it is also one of the most expensive. I also like to use an inside-round roast barded with pork fat.
Cooking methods will vary depending what kind of sandwich you want. The classic philly style is first shaving the meat thin (if you don't have a slicer, partially freezing helps cutting thin), then sauteing with perhaps onions.
Me? I like a crusty bun dripping wet with juices, so I make a braise to get plenty of that 'juice'; barded inside round roast, brown on all sides in a dutch oven. Add beef broth, S&P, and paprika, and perhaps 'browning' for color. Braise for a short time, bringing the roast to med-rare. Remove, let rest.
Slice meat very thin, cut roll in half, dip in braising liquid, layer meat, put a few pieces of the bard fat, and voila...heaven on a bun.
If you want the meat cooked more, simply drop the slices in the braising liquid for awhile.
I'd agree with gg, and suggest a dry roasting.
I like the brown crust and would pan sear first. I also like the meat more on the rare side, so I roast at high temp for a short time. I've done this with entire round roasts (11 pounders) then fridge overnight. The meat sets up nicely and you get beautifully rare slices through and through.
A long slow roast might be better for a more thoroughly cooked meat.
Oh yeah, my fav is indeed french dip style (with the pan juices dripping out the side down my chin and wrists....lotsa paper towels)