It depends on how you are preparing it. If the tenderloin being oven roasted (slowly is preferable, but that is a separate issue) and then sliced into servings then being finished with a sear. (IMHO the 'right' way to do it) then it 'should' be called a "Beef tenderloin roast", mentioning the sear is optional.
To be a steak the tenderloin is first sliced into servings and then grilled, broiled or pan fried. A 'steak cut from the tenderloin' is called a 'filet mignon'.
Most commonly a banquet will opt for the first option as it is easier to prepare en mass, and that is what it sounds like you are describing, so I would go with "Tenderloin Roast" to conserve space, I doubt anyone expecting something slightly different would not be bothered by the difference. If you want to be more specific, consider "Tenderloin of Beef"