Beef knuckle is the standard name for a roast from the round. Its marketing term is 'sirloin tip roast', even though it is not from the sirloin.
It cooks like other round cuts so, yes, is used for roast beef. It is not at all like a chuck roll. Knuckle should be cooked to low or moderate internal temps and sliced very thinly after resting. Chuck roll is, well, chuck, and should be cooked to a till fall-apart tender, or at least quite nearly so. It can be puled for pulled beef. Knuckle is not suitable for that.
If you search for sirloin tip on the board you'll see quite a few threads and posts about them.