Copycat Arby’s Roast Beef Sandwich

1) Roast the beef

1. Heat oven to 300°F. Set a wire rack over a rimmed baking sheet if you have one.
2. Pat the roast dry. Rub with olive oil. Mix salt, onion powder, garlic powder, paprika, and pepper, then coat the roast all over.
3. Roast until an instant-read thermometer hits 125°F to 130°F for medium-rare, about 60 to 80 minutes depending on thickness. (If you prefer medium, pull at 135°F.) Carryover cooking: expect the temp to rise about 5 to 10°F as it rests, so pulling on time matters.
4. Rest the roast 20 minutes at room temp.
5. Then refrigerate 2 to 3 hours until firm for thin slicing. For deli-thin slices, do not skip the chill. If you are in a hurry, freeze 25 to 35 minutes instead.

2) Make the horsey sauce

1. Stir mayo, horseradish, vinegar, sugar, and salt in a small bowl.
2. Taste and adjust. More horseradish for more bite, a pinch more sugar if you want it rounder.

3) Make the cheddar sauce

1. Melt butter in a small saucepan over medium heat. Whisk in flour and cook for 60 seconds.
2. Slowly whisk in milk. Simmer 2 to 3 minutes, whisking, until slightly thickened.
3. Turn heat to low. Add cheddar and American cheese (if using) a handful at a time, whisking until smooth. Do not let it boil after the cheese goes in, or it can turn grainy.
4. Whisk in Dijon, garlic powder, and salt. Keep warm on the lowest heat, stirring occasionally. If it thickens, splash in a little milk and whisk smooth.

4) Optional au jus-style dip

1. Simmer beef broth with Worcestershire, onion powder, and pepper for 5 minutes. Taste and adjust. (This is a quick au jus-style dip, basically a seasoned broth meant for dunking and warming the beef.)

5) Slice the beef thin

1. Place chilled roast on a cutting board.
2. Slice across the grain as thin as you can. Look for the lines of muscle fibers and cut perpendicular to them. Aim for deli-thin. If slices feel thick, you can stack a few and slice again to thin them out.

Little trick: If you want that super tender, steamy fast-food texture, dunk the slices in steaming hot au jus-style dip or broth for 20 to 40 seconds right before building the sandwich. For anyone who prefers a stricter food-safety approach (or if serving kids, seniors, pregnant people, or immunocompromised guests), reheat the beef to 165°F.

6) Toast and assemble

1. Split onion buns. Butter cut sides lightly and toast in a skillet until golden.
2. Spread horsey sauce on the top bun.
3. Pile warm roast beef high on the bottom bun (about 4 to 6 oz per sandwich).
4. Spoon or drizzle warm cheddar sauce over the beef. Cap it and serve. Add au jus-style dip on the side if using.

Fast deli-roast shortcut (10-minute version)

1. Warm 2 cups beef broth in a saucepan until steaming hot, not boiling.
2. Dip deli roast beef in the hot broth in small batches for 20 to 30 seconds, then lift out with tongs.
3. Toast buns, add horsey sauce and cheddar sauce, and stack the warmed beef. Done. If you want the beef fully reheated, keep it in the broth a bit longer and heat to 165°F.