Hi Jude, since you don't know what kind of roast you have, it might be best to cook it in a crock pot to ensure it gets tender. Some cuts will be tender just dry-baking in a roasting pan in the oven. But the less tender roasts need long, slow moist cooking for them to get tender.
Those cuts do great in a crockpot. I like a boneless chuck roast. The roast, beef or pork, will be fork tender and will easily shred.
I pat it dry then rub it all over with a very light coat of olive oil. This helps the seasonings stick. I sprinkle with salt, pepper and a little garlic powder, place in crockpot then add a can (or two) of cream of mushrom soup, cover and cook on low for 6-10 hours, depending on the size. Sometimes I use cream of celery soup or one each of mushroom and celery. Makes a great gravy.
Sometimes I rub with pepper, no salt, put the roast in the crockpot and sprinkle dry onion soup mix over roast and add soup. For a large roast I add 1 pkg and 2 cans of soup. For a small roast, I add 1/2 pkg and 1 can.
If you don't like cream soups, this makes a great gravy. I know it sounds strange, but it is one of our favorites. Put 1/2 cup water in the bottom of the crockpot, place roast in crock pot and sprinkle with a pkg of dry ranch dressing mix, a pkg of dry Italian dressing mix and a pkg of dry brown gravy mix. Cover and cook on low 6-10 hours. The gravy is wonderful!
Sometimes I add potatoes, carrots and onions the last 1-2 hours. The larger the pieces of carrots, the longer it takes to cook them until fork tender. Cubed potatoes and onions get tender in about an hour.
We love pulled pork (and beef) BBQ. I season a pork loin, boston butt or boneless chuck, put in crockpot with 1/2 cup water, pour a little BBQ sauce over meat, cover and cook on low for 6-10 hours. Then I remove roast, discard liquid, shred the meat and add BBQ sauce. Great for sandwiches.
One nice thing about crock pot cooking is not having to worry about internal temp. LOL But to answer your question, the internal temp of a beef roast should be 145 to 150 for medium and 155 to 165 for well done.
If you cook a roast just until it reaches a safe eating temp, it can still be very tough. But long, slow moist cooking causes the fibrous connective tissue in the meat to break down. That is why it will shred easily with a fork.