Roast beef? I’ve done some large roasts on the grill yes and I do them until they are medium.
On the 165 degrees…. Since the brisket has a thick end and that’s where the temp is read, the thinner portion will be higher in temp as will be the outer areas of the thick end. Wrapping in the foil, shiny side in, traps the heat and reflects the higher temp on the outside inward where it will continue to rise on the inside for a short while before the thick end begins cooling. I’ve never bothered reading the temp inside after the meat gets sealed but the thin end and the outside layer of the thick end of the brisket will be roughly 185-190 degrees when the meat gets wrapped.
As mentioned I can’t eat rare or bloody meat. At a 165 reading in the thickest area there it still some free blood and quite pink. I wrap the foil, shiny side in, tight on the meat as soon as it comes off the heat. When its completely room temperature I put it in the fridge overnight. When I slice it the next morning it is free of any blood and pink but is still juicy. The key is to stop the actual cooking process while there is still some pink and allow the higher heat in the other portions of the meat to finish the cooking inside the foil.
Also, when I slice the meat, I figure out how much I need for the crock pot for the 4th and set it aside, then package the remaining sliced meat in 1 pound vacuum sealed bags and freeze. I thaw those still sealed and use this meat for my sandwiches. And I use only Campbell’s beef broth for the crock pot meat. I know the assumption can be made that beef broth is beef broth but I’ve tried some other brands and can tell you nada. If there is meat left over in the crock pot after everyone has their fill [not a very regular happening] I drain the broth off and bag in a zip lock for the fridge.
I should also note that I do not do a mess of rub stuff on my brisket. Rubs have a ton of refined salt in them and the salt will pull moisture out of the meat. I want the moisture in the meat. I have made rubs using brown sugar and some seasoning spices but as a rule I do not put anything on the brisket prior to the cooking process and I don’t baste it ever as I want the bark to develop continuously without having to re-dry after adding a baste. When the brisket rests wrapped in foil the tough bark will soften up nicely so it can be cut thru when slicing.