1 well-trimmed beef ribeye roast, small end (4 to 6 pounds)
1/2 cup Dijon-style mustard
2-1/3 cups cheese and garlic or Caesar croutons, finely crushed (about 1-1/4 cups crumbs), divided
1-1/2 pounds green beans, trimmed
1 tablespoon olive oil
Heat oven to 350F. Spread mustard evenly over all surfaces of beef roast. Press 1 cup crouton crumbs evenly onto roast over mustard.
Place roast, fat side up, on rack in shallow roasting pan. Insert ovenproof meat thermometer so tip is centered in thickest part of beef, not resting in fat. Do not add water or cover. Roast in 350F oven 1-3/4 to 2 hours for medium rare; 2 to 2-1/2 hours for medium doneness.
Meanwhile toss green beans with oil on metal baking sheet. Add remaining 1/4 cup crouton crumbs; toss to coat. Roast in 350F oven with beef roast 30 minutes.
Remove roast when meat thermometer registers 135F for medium rare; 150F for medium. Increase oven temperature to 450F; continue roasting green beans 10 to 20 minutes or until tender and starting to brown.
Transfer roast to carving board; tent loosely with aluminum foil. Let stand 15 to 20 minutes. (Temperature will continue to rise about 10F to reach 145F for medium rare; 160F for medium.)
Carve roast into slices. Season beef and green beans with salt and pepper, as desired.